I would not use beadliner on the frame or underside of a car. Im
Sorry but I just hate that and actually think it looms cheap. I would only use it if my underside is beat up want to cover blemishes etc... Thats right it will cover bolts, holes, lines , etc and is gunky when trying to remove bolts etc. If your frame is fairly new just use a chassis satin black on it.
If you still wanna go the bedliner way stay away from roll on types and rhino, herculiner. I would rcommend Raptor or SPI. Both sprayable 2k