Just like Foe, I also did rj_rocketeer as an Engy, but without any HP cheats. Got to stage 13 which I could only do half way. <.< I skipped that and did the last jump normally. I also did skyscraper, but used impulse 101 on it to save time. I can do it without that too. Just need a lot of teleporting.
Also, Ramp posted the right way to Engy jump. It's hella hard to pick that sentry up with you.