is a link to my build thread. Page four has some references to how I bent the drop loop. I used two pieces of 3/4" MDF fiberboard, routered both pieces with a 45 degree chamfer, screwed them together to create a channel for the pipe. I tightly packed the tubing with sand, and cold bent the tubing. I got a little tube distortion, it flattened out a little, but no kinks.
I don't have any dimensions for you, but I just measured the height of my engine, located where my crossbar would be and figured out how deep my loop needed to be.
I have also used a conduit bender tool with ok results, but access to a mandrel bender would be best.
Hope that helped,