Justed checked my mail and i got an answer from Tony Nuskin at premapro and i think it might be of interest to the SOF folks.

Based on your email I am going to make a couple of assumptions.
You already have some flavor of Epi varnish applied to your SOF boat.
You are probably using one of the mid weight poly fabrics (6 – 8 oz).

Coelan has been applied on several occasions directly over exiting varnish. However this is usually on a section of wood (mast, transom, railing). I’m not aware of any first hand data regarding Coelan over varnish on a fabric surface. That does not mean someone somewhere has not tried it.
The criteria is for the varnish to be “perfect” in the strictest definition of the word. Any cracks, crazing or lifting of the in place varnish will greatly compromise the life of the Coelan overcoat. In other words as the varnish cracks and lifts so will the Coelan overcoat.
Many boat or yacht owners have contributed incredibly hours into the prep and varnishing of their project and I can appreciate there reluctance to remove all of that hard work. I can also predict that the removal of any varnish or paint from a fabric weave will be darn near impossible. So, therein we have a dilemma.

Here is what I recommend you do and again assuming the existing varnish on you SOF project is in tip top condition, I would suggest you get a small tin of the Coelan transparent gloss coating (375ml) and find a suitable test surface area or section of the kayak. Clean/wash the existing fabric well (no solvents) and then apply a few coats of Coelan. See how it stands up and if the results meet your needs over some reasonable time period. If the test case works out then you can proceed to apply Coelan (probably 3 or 4 layers) over the remaining surfaces.

In an ideal world both Coelan and Premapro always advocate applying Coelan over a well prepared (primed if necessary) surface, free from existing paint, varnish, grease, dirt etc….) We would also suggest the use of one of the Coelan Flex primers as this component has the UV agents that help protect the substrate/fabric from solar ray damage. I do know that some of the SOF users have chosen to skip this step but that is their decision and time will tell if it is reasonable.

BTW: It should also be kept in mind that despite best efforts on the part of the chemical engineers at the Coelan factory in Germany that it is impossible to take into consideration the product and chemical compatibilities with other manufacturers formulations and various end users application decisions.

After an application of one of the Flex primers (the difference being if you are going to color or pigment the Coelan coating or not) then apply your first Coelan coating layer working it well into the fabric. When that layer dries to touch you can then continue to apply the necessary additional layers. We suggest five in total ( 1.0 mm combined thickness) but again I do know some of the SOF community has decided that three is sufficient. Here again, time will tell.

Our objective and in keeping with Coelan factory instructions is to ensure the user receives the very longest applied life of the coating and that is why we always defer to factory user instructions. (Downloadable from our web site) Coelan has adhesive like properties and the bond between substrate and first coating layer is a mechanical one as well as a chemical one and the primer of choice helps to facilitate this. The same mechanical bond, via the proprietary Coelan formulation, is also true from one layer to the next. The end result is a long life, UV resistant, flexible and one way water vapor permeable coating.
Despite misleading advertising to the contrary, Coelan is the only coating available that provides all of these characteristics.

From my end as a user and long time boater I would much rather be sailing than varnishing and that in part is what led me to begin importing the Coelan products several years ago. Our higher volume users (Royal Caribbean Cruise Lines for one) agree with this concept completely. The time and labor (and money) saved in routine touch up and maintenance of existing varnished surfaces is why some of their vessels made the switch to Coelan a few years ago. (Pictures available)

I wish I could give you more first hand experience based data with respect to SOF fabric and Coelan applications. I have used it on several high quality neoprene/hypalon based inflatable dinghies (Avon, Achilles) with great success. And I do occasionally receive positive comments from some in the SOF community. Perhaps I should take the initiative and email a request for some user feedback on the SOF web site blogs. Being a plastic kayaker, I’m a little hesitant to step into the craftsmanship and dedication that the qajac community represents, nor do I wish to be viewed as trying to sell more product. However detailed, specific, feedback is important to us.

I hope that the above information is of use to you and certainly if you have any additional questions or comment please do send me a direct email and I will be happy to reply. My philosophy has always been to work in honest partnership with our clients and ensure we both enjoy the best chances of success with our specific projects.

Now that's what i call a good and decent response, many a customer services could learn from this, especially epifanes holland as they've just about ignored my questions regarding sof.