Manna PE/5 to PE/9 without Stall bars?

Manna exercises PE/5 - PE/9 are various forms of leg raises on stall bars. I don't have stall bars - the closest I can find is at the playground where I can find a few bars that resemble stall bars that are each almost a couple feet apart. I've tried doing the exercises on these, and I feel it puts a lot of pressure on my shoulders (my arms have to reach back behind the plane of my body to grab the bar)... Feels potentially unsafe, though perhaps I can ease into it gradually.

Alternatively I've tried doing it just hanging from a bar, but this seems like a much different exercise.  

Any guidance? Thanks!

I've been without stall bars for years (getting some in a few weeks!) but there's some alternatives.

1. If your shoulder mobility in flexion is good, what you are doing now shouldn't be a problem. If it's not, try spending some quality time doing dead hangs from the playground bars.

2. If you have a partner they can just push on your shoulders/upper back from a regular bar. It's hard to keep you steady though.

3. Improvise. I've done these using a peg board, as well as the support bar of a crossfit type rack (support with two pullup bars on each side, with my back on the support. I can see these happening with a door pullup bar if the door can be closed, or rings/trx hanging from a sturdy closed door. Worst case, do them from a regular bar (try undergrip) while you wait for stall bars to ship

Hope you find something that works for you!