BTW, The only Laurie I have ever known in 71 years did not run on CNG or any other kind of G.
A suitable fuel system would require an accumulator the size of the Hindenburg. Tethering would be an insurmountable problem to begin with, especially if done on the counterweight and the steer axle is unloaded due to uplift. One could let their imagination run wild. There may, possibly, be a role for Scottish bagpipes in this scenario, however. A 4 stage mast at maximum elevation with a max capacity load cannot have improperly dampened surges. And, I would add, that a properly dampened surge under this condition is a risk of testing the overhead guard anyway.
Yes, triumphrider, biogas. You can run a lorry designed to use CNG on it so I am wondering if this would be possible with a forklift, with a suitable fuel system of course.
Surging would be unacceptable.