Steve,

A process I have seen used in bonding laminate to bench tops where contact cement is the adhesive is to use a series of dowels (about 1/4 to 1/2" diameter) spaced at about 2-4 inches apart to keep the two contact coated surfaces separated until the positioning is correct.

Starting at one edge or one corner, you then remove each of the dowels by sliding it longitudinally and allow the adhesive coated surfaces to contact each other. If the dowels are not positioned until the adhesive is tack free, they will not adhere to the surfaces and can be moved easily.

With a minicell seat in a kayak, this should work if you remove the dowels under the bottom of the seat first, then the ones at the side. To eliminate any gross misalignment it would be best to use a larger number of smaller diameter dowels, say 1/4 inch at 2" centers.

Should work,

Good luck, Ron