Looks like it'll be a solid rifle. You've obviously put much time, thought, and money into this build. I say go ahead and spend another $120'ish and get a 20 MOA rail base. You'll be glad you did. IMO, no need to get proficient with the rifle under one set up, and then have to learn again once you alter the set up when adding the 20 MOA base in the future. I also prefer to have the scope as close to the barrel as possible, and I think you can get away with low rings if you have the 20 MOA base, even with the 50mm bell (you'll want to double check my math). Btw, I'm a HUGE fan of Vortex glass. I have the Vortex Razor HD 5-20 EBR2 Reticle Mil/Mil with a 20 MOA rail from Nightforce and Low rings from Nightforce.