Mr_Flibble
In Tabulas Argenteas Refero

Leica M-E with an early 5cm f/2 Summitar.
Leica M-E with an early 5cm f/2 Summitar.
Great, 42mm clamp on work well on all this lens, summitar included��
I'm seeing the ITDOO hood as a more compact alternative too the SOOPD. Not cheap though It looks like it clamps on similarly as the Barn-door hood. So you'd probably have the same issue with it.
A screw-in hood might a better option. Though, I'm not sure there are any in that thread size.