[Arct1k]

Not required for stopping the end bell from falling off like a Feigao and temps should be ok.

However it would help with stopping dirt from getting into the open end and would provide extra surface area for heat dissipation.

I run an S HS on my 50mm & mike ran a L on his 60mm - The XL would fit the 70mm perfectly with a neu front cover or be slightly too long 4mm without - Or you could use an L HS and have 10mm uncovered.

or you could just use a clip-on if required. Lots of options.