: Any suggestions as to sources of heavy duty velcro? I want to make the seat
: and other minicell outfitting on my Night Heron removable.

Len, the problem with Velcro is getting it to adhere properly to the surface you're bonding it to. Specifically, the "hook" portion is made of polyethylene and has a slick back surface, so it's difficult to get a decent bond. Unless you're willing to invest in expensive specialty adhesives to bond it, you will likely be disappointed with the results. The "loop" side has a woven (Nylon?) back that works well with almost any adhesive and I've never had issues with it.

I've used the self-adhesive, "Industrial Strength" Velcro (from Home Depot and other sources) and what I've found is that in a moist environment, the bond weakens over time and eventually fails, sometimes surprisingly quickly. In cold weather, it's common for the "hook" sections to completely separate from the adhesive, leaving the latter on the surface, where it can be a real pain to remove.

Another thing to consider is that if you make the seat removable, you can't prevent sand from getting underneath it and abrading the hull as you paddle. A bonded-in seat can be sealed around the edges.