It's significantly easier with shorter straps.
Regular straps (~10') compared with straps that are about 3' in length the difficulty doing it on the shorter straps is probably about 70% of doing it on the real thing.
30 degrees above horizontal on short straps you're maybe 40-50% of the way to full cross at max. The and sucky part is that it gets significantly harder the closer you get, and strength gains come slower.
That's why it's a 1-2 year project even at good strength to bodyweight ratios (130-160 lbs range).