7xl running on 5000mah 25c lipo

wow. I don't know what to say about those lipo's. Maybe just "good luck". I personally would not have bought those, and I definitely would not trust them for 125A. 8xl on 4s should pull less than that by a good bit though. You might be alright. Watch the temp on those batteries. As long as they stay cool and don't get over-discharged they might be alright.

J.