Say you set the output to 30V@17A.
If your raw DC is 40V, then Pd is 17*(40-30)=170W
If your output is say 1V@17A then that will rise to over 650W!
TIP35s max Pd is 125W and that’s assuming you can keep Tj somewhat under 150'C. More like 100'C tops.
That will need seriously deep sinkage and ferocious fanny action.
www.ppi-uk.com/heat-sink-calculator/A buck pre-regulator tracking a above the dropout voltage for the linear reg will save you a heap of expensive hardware.
It will make for a much more robust and reliable PSU. TIP35s are only a couple of bucks a piece, use more of them to help stay cool.
You've just saved on a monster fan and heatsink so why not push the boat out?
Consider modding the circuit to use MOSFETs
Watch Dave's series on LAB PSU design