After chewing on it overnight... i've decided to bump up the tube size a notch. It's just a little too springy for my taste, and considering I'm going to have a harness wrapped around it, I'd prefer it to be a little stiffer. So I'll use the tube thats there as a sleeve to get it up to size, chop the middle length out and slip fit the next size tube on.
Quick maths says for a 100kg load at the center on the current beam, I've got a 33mm deflection @ 9500bar (sounds about right having stood on it)
Simply stepping up a size tube (same 1.5mm wall thickness) drops deflection to 22mm @ 7300bar
And just for kicks, I roughly looked at having the harness installed offset from the middle of the the beam (200mm offset from the center) and looked at a 20g crash. Assuming 1/3 of my 100kg body weight would be held by the shoulder harness, that's a 600kg load... Gives a 29mm deflection @ 26000bar (vs 43mm with the current tube size).
So next size up it is

Woven 3k carbon tube over the top (1.5mm wall) will halve that again if you believe the numbers, but I'd rather not rely on it
Edited by Doctor Ed, 13 August 2016 - 09:22 AM.