I build all my projects using Baltic Birch plywood. I like there are few if any voids and at least one side has no imperfections. For years, if I bought a piece of plywood marked as 1/4" thick, it was 1/4" thick. The last two times I bought plywood none of sheets of plywood were the exact thickness as advertised. It now appears that there is no plywood available in imperial inches (1/4" for example). Instead, it appears all plywood manufacturers are making plywood using metric dimensions. Recently, I built the Jeep Grand Wrangler using the plans designed by Lloyd Watson and sold here on the Toymaking Plans.com site. The plans called for 7 1/2"pieces of some material to make the frame of the body. Using the 1/2" plywood I had, I cut out and glued up the 7 pieces only to discover I was 1/4" shy of the necessary 3/ 1/2". I cut out two more pieces out of 1/8" stock to make up the differences, but that now meant I had to glue up 9 pieces of stock to make up the body. Trying to manage that many pieces to get a reasonable clean line over that whole piece is difficult.
All of this rambling is to ask, should the designers now start giving its directions in metric rather than imperial-inch? Mr. Watson's plans may have started out using metric measurements as there are many mistakes in the plans particularly involving the diameter of some parts that need to be drilled for matching dowels. (see xihunter posts) Just converting all the imperial measurements to metric doesn't necessarily work as I found out with the body of the Jeep.
Turning the question directly to you, Mr. Lewman, since there is not any imperical-inch dimensioned plywood stock available, should you adjust your plans to reflect what is out there for the toy builders to use? If it is known that when you call for a 1/4" piece of material to be used in one of your plans, then the plan calls for a 1/8" hole to be drilled in the thickness of that piece of material, even if the stock is a true 1/4" there is little room for error. This further complicated when that 1/4" piece of plywood is not 1/4", but something close to 6mm. Do I try to drill the 1/8" hole, or switch to metric drill bits and compensate when the 1/8' dowel no longer fits. I don't know where one finds dowels in metric sizes.
I really enjoy the plans offered on this site. The detail for most of the plans make them fun to build and produce a project I can be proud of; however, this plywood issue is becoming an increasingly frustration problem.