I have some input on the holey frames. I did the same to cut down on weight. When all was said and done, I wish I would not have done it. I weighed all the little disks I cut out and they added up to about 1 pound. However, the additional work required to be certain that all edges of the plywood were sealed in case water got into the underside (and it has due to hatches being open out in the rain) was not worth the 1 pound in savings IMHO. The cutouts that Matt specifies in the plans allow access where I needed it. I made the two on the side frames near the front of the cockpit larger and more square rather than the arch the plans called for and I can get plano and shimano tackle boxes into the sides and under the seat. I did double the plywood up in a small area where the square hole is cut to make up for the loss in strength.

If I remember correctly, I can get six tackle trays in this way. single stacks on the sides, and double stacked under the seat. However, i have to some times remove a couple to get to the one I want. I also put a small 4 inch hatch between my legs in case stuff slid way back under the seat so I could push it back forward. I used an 8" quarter turn hatch from Duckworks.
Here is the link to how I did it.
viewtopic.php?f=8&t=2811&st=0&sk=t&sd=a&start=30
I added the foam mesh drawer liner stuff from Harbor Freight (or any of the other department/hardware stores) to the below deck floors to keep things from sliding and to keep things quiet.
http://www.harborfreight.com/cpi/ctaf/d ... mber=67055
I wish I would have done recessed handles like Bemm. I just used store bought ones and I wish they were stiff an non- moveable like he did. I think it would give me a better grip.
As for the depth of the tank well, I believe the tank well is near the water line so any deeper and you may be towing around additional water. You could make a custom insert like Hairy Mick did for his Okwata
viewtopic.php?f=8&t=2501&start=90
I may do this to make an insulated fish box.
I hope this helps you.