Henry Cardwell.. Most of my covers are made of Advantec. I use them as a migratory top, and as feeder tops. I only use an outer/telescoping cover in late Winter or if Summer is very hot, just for insulation.

Different manufacturers make their equipment to different specifications. There is variation between length and depth between different companies. For instance, Some companies have the bee space at the top, others at the bottom, so depth can vary as much as 1/8 to 1/2 inch. It is good to have all your equipment the same, otherwise, you will get bridge comb, and, propolis buildup between top bars and bottom of frames. Kelly uses 9 7/8 for depth, while some companies use 9 5/8. The rabbet cut on the front and rear is also different between companies. Normally not a big problem, and it depends if the wood shrinks any after they cut the components.

There are no stupid questions if you do not know the answer. Don't ever feel embarrased to ask a question.

As for squaring the boxes. Nail or staple gun the two ends, or the two sides, (whichever way you assemble your boxes) then use a regular carpenter square to square the box by placing pressure on the side/end that is out of square, then nail or staple the other side/end. I find it easier to square after one haft is nailed rather than trying to square before nailing.

I can't think of any reason to be concerned with the equipment you currently have in use. If they are slightly off from kelly boxes, no big deal. They will still work. At worst, just a little bridge comb or propolis.

Hope this is helpful. If not, contact me at cchoganjr@scrtc.com and I will try to help you.