My batting is on the dead bar. it is folded in half and measures 98 wide when unfolded. I usually take the Measurement of my quilt and if it it below 90", I just unroll the batting up and over my longarm until I have the length needed. I use batting scissors and follow one of the bars to keep it straight. Rarely do I try to use a rotary cutter the trip batting because there is always a factory edge.
PM me if I can heelp further.