Radio ROM question

[joojoobee666]

Ok, my bootloader is at 2.40, and a I'm running a "cooked" (is that the correct word?) rom of no2chem's 5067 using ppckithcen's app. My GPS takes about 10 minutes to lock on after a reboot/soft reset. After that it locks on within 10 secs...until another reboot. I'm thinkin this is from the 3.42.30 radio rom. If I want to downgrade my radio rom, do I need to anything special? Can I just put my phone in bootloader mode and flash it with without worry? (sorry, i'm kind of a noob). I've done some searches but just have't been able to get the right answer. Can any1 advise? Should I even bother downgrading my radio rom? (was thinkin of 3.39. I'm VZW and a lot of peeps say this one works great for them)