MIMF

I'm making a 000 acoustic. I've read that backs should have a radius of 20' or less, and tops should have a radius of 25' or more. Is there a problem with using a 25' radius for both top and back? What is the downside of doing the same radius (25') for both?

No problem using the same radius for top and back. Some people find a more strongly arched back aesthetically pleasing, and go with a tighter radius.

I use the same radius for top and back, probably at least 25', but it is pretty approximate. So far, so good.

I use the same top/back radius quite a bit, and although it was initially a 24' radius, it might be a tad tighter now. I'm intending on redoing my jigs pretty soon to be a bit more exact.

A couple of things to keep in mind are the neck angle (or elevation above the top) needed to maintain your preferred bridge height and the extra stiffness the arch will be imparting to the top. Ideally this should give you the option of thinning the bracing a bit relative to a flatter top. I have a specific deflection target I try to meet no matter what the top arch might be.