Angie, here is my take on 40 in a single stack.
If you reload, good deal. This is the biggest single factor.
If you are building a gun for the Single Stack Classic, where mag length is an issue, good deal.
If you don’t reload, bad deal.
If you are planning on shooting USPSA Limited 10, bad deal. L-10 doesn’t care how long or fat your mags are, just don’t put more than 10 rounds in them. Nobody makes a 10 round mag in 40. Some 45 mags will work, but they may take some tweaking to get it right. Even then, they might not be 100%. Using factory mags you end up shooting Limited-9.
All that said, I like mine. Its built on a Caspian Single Stack Race Ready Frame and a Schuemann AET barrel. I gaffed off the Bomars and went with the Heinie low mounts. I haven’t had any problems at all other than it doesn’t like ammo loaded longer than 1.180. I am now load all my 40 to 1.169. I use CMC 10mm mags.
Good luck to you. I hope I didn’t muddy your water too much.
Tom
AF Shooting Team