Just finished making mine..I did a couple things differently.
Instead of having the pipes with the rubber feet sit directly on the carpet I made a 'peg' system block like the ones used in the back - so that the weight is evenly supported onto a 3.5"x3.5" square block instead of resting completely on the pipe foot.
I also raised the back an extra 2 inches by attaching a 2x6 plank to the bottom of the back leg supports so that the whole rig is flat. With your measurements there was a decent up (back to front wise) slope on the middle/front pieces because they had to go up to clear the seat bottoms.
Another side note - I'm not sure the turn buckles are entirely necessary...I used them too in my build but I don't think you really need them.
Your write up and design was really helpful..glad I found this before I tried to completely design one myself.
Instead of having the pipes with the rubber feet sit directly on the carpet I made a 'peg' system block like the ones used in the back - so that the weight is evenly supported onto a 3.5"x3.5" square block instead of resting completely on the pipe foot.
I also raised the back an extra 2 inches by attaching a 2x6 plank to the bottom of the back leg supports so that the whole rig is flat. With your measurements there was a decent up (back to front wise) slope on the middle/front pieces because they had to go up to clear the seat bottoms.
Another side note - I'm not sure the turn buckles are entirely necessary...I used them too in my build but I don't think you really need them.
Your write up and design was really helpful..glad I found this before I tried to completely design one myself.