I`ve no doubt SDM are tougher and perfectly OK on some sails (ie the ones designed for them) but I`ve given up on them !!!
Found both my NP and Tush (Search and Rocks 4.2 to 6`s) when rigged on SDM can hang on for another 5 mph wind or so.Initially and when moderately powered sails felt fine on RDM but when really pushing to max they definitely break up earlier than when rigged on equivalent SDM. They need longer booms on RDM and downhaul tension is less .
And I dont care what anybody says (or that IMCS says differently) RDM are NOT as stiff on equivalent lengths as SDM.
I can rig my 7.5 (GTX) on a Tush 75 430 with a massive extension and it feels ok. (not ideal) but try same with a RDM and its feels more like its rigged on a fishing rod. And my 430 RDM is 100% C !!!
Lay a 430 RDM and SDM out together over 2 stools. The RDM is definitely more flexible ! (Perhaps the Tush 75 are over stiff ???)
My RDM `s are now the spares and only use them reluctantly !!! (But I weigh 105k)