Oh, thanks.
Sran dualdrive increases the gear ratio dramaticaly.
For my calculations, i see his setup with sran dualldrive 53t crankset and 11-? would take him up to 177 gear inches on his heavyest gear.
177 gear inches is archived on smallwhell folding bike with an regular setup with 72t chainring on front and 11t cassete on rear. Wich is very high.
To archieve 70km/h with that gearing the he should be at 120rpm cadence.
The frame would flex so mutch that i think is impossible to folding bike.
Even dahon 30 anny or other premiun terns or multons cannot hold this forces.
Pehaps with an recumbent? Or with a pod fo avoid air resistance?
My bet is that his archieve this speed at an botton of a huge downhill, not on flat.

Best,
pedro