Ugh, I hate crawlspaces. Ours is tight like that. We just had a new furnace and ductwork done last year, so the new ducts block my old spot to get to the master bath plumbing. Had to repair a pipe this year, I had to bring a small shovel and dig a small tunnel to get myself under a beam.
I'd insulate ours but at this point, we ar emoving in about 2 years, so I don't think it'll be worth it.