For my Osprey, I used a 4x8 sheet on the floor when joining up the panels - the extra width allowed me to do half the boat at a time. Then I ripped the sheet and joined it into a 2x16 table with 2x4's underneath. Set it on a couple of sawhorses. After the boat came together, I used some surplus roof rack saddles to help hold it in the various positions needed. Stayed on the table thru the whole build - always a handy place to set tools, cups of epoxy, etc.

You might could use the borrowed tables as the base, clamping the ply on top to protect and help flatten the worksurface.

There doesn't seem to be much collective knowledge on the WD kits - will be interested to hear of your experiences.