Yes any of the manufactured troughs can be used..."approved" refers to a quick check in the morning of the tournaments to make sure it's not a home made device with their own "short" measurements.
Hopefully Andy at OEX and a few of the other kayak dealers and tackle stores will be stocking them soon. The Hawg Troughs can be found online easily.
We will also be giving out a velcro band "the morning of" that can be used to restrain the fish.
