I think you might be overlooking another way to limit yoiur boards speed and making
it easier/safer to get into the back strap.
What would happen, if you didn't sheet in fully as soon as you hook in.
If you don't continue to sheet in, your speed should stay fairly constant, and
allow you to settle things down, at much less than full speed, then get your foot
in the strap.
I tried this yesterday while sailing the Futura 133 with the '08 Retro 6.5.
The wind was strong enough that I was getting tossed over the forward lee side
doing beach starts, so there was plenty of power in the rig.
What I found was that I did not want to (or need to) sheet in fully.
If I only sheeted in enough to support my weight, hooked in, and with the front foot in the front footstrap I could sail along nicely with my back foot on the center line and just forward of the rear footstrap.
I dould sail along at much less than full speed.
When I was ready, I moved my foot out to almost standing on the front of the outboard
rear footstrap, then placed my foot in the footstrap.
As soon as I was fully in the strap, the rig was raked back fully and sheeted in a little more, the speed increased noticeably, and the board went to full speed.
I cannot stress enough to you guys that you do not need to be in a hurry during this evolution.
Yes, I know, you think the board is going to gain too much speed and you will have problems/get catapaulted if yoiu don't get hooked in, sheeted in, and in both footstraps quickly.
If you use the sheeting angle of your sail to moderate the power from your rig, you should be able to do the whole evolution at a much slower and more comfortable speed.
This changes a bit is you are only moderately powered and have to wait for boardspeed to develop, but as I said before, in moderate conditions you need to be very careful not to oversheet because it's very easy to do, and shuts your speed right off.
I hope to try all this again soon and get back with your.
Wish I had a video to send you that breaks it all down into steps.
Hope this helps,