Would you consider shaving off a bit of the width of the C brackets when you have the next batch made? They are just a bit too wide to allow connecting the U channel right next to them.
For instance, I am using a 3" U channel for the body of The BiPod and Mega Scout. I have the Pan/Tilt turret attached to the one end of the U channel using an ASB-18 interconnect bracket, then two short C brackets for attaching the upper legs.
There is not quite enough clearance to attach a U channel behind the C brackets. It is so close though and would not require shaving much off the width of the C brackets.
On the BiPod Body (a 3D PDF), the U channel is at the back. I wanted to mount the U channel where the long C pointing up is, but there was not enough clearance.
It is so durn close. Maybe I can file the sides enough to get enough clearance, but I would prefer to not do that. I don’t care to make modifications if not necessary.