I've built 3 kayaks now out of the cheap stuff, 2 completely out of 1/8" doorskin type mahogany plywood and one with a 1/4" (5mm actually) hull and an 1/8" deck. What I did is look at every sheet they had and picked the best ones by looking at the edges for voids and the outer veneers for flaws. In one case, I didn't like any of the sheets they had and waited for their next shipment.

There is always a chance you will get a sheet with a void which will cause it to bend unevenly or break, but you should find this out when you cut out the panels or when you stitch the hull together. At this point you have really only invested time and money for the plywood. At less than 25% of the cost of Okume you can start over 3 times and still come out ahead, but I've always ended up with a kayak the first time. It is also a lot less stressful to cut up a $20 sheet of plywood than it is a $90 sheet.

I don't really know anything about other types of plywood and I don't think there is any practical way of fixing a sheet with voids.

: Have seen some argue not even to use the stuff, but availability of Okoume is
: going to run me about $90/sheet or more here in AK to order (after
: shipping).

: If I were going to use luan doorskin type material, can you tell me how to
: tell if a given sheet of luan is "good stuff." I've seen
: reference to void-free, or voids filled on this and other sites. How do
: you tell, or fix?

: Are there other products I should consider? I was told of another ply with
: MDF? core, also avail in 1/8".

: Thanks