I'm a bit surprised about some statements over Hot Rod masts from Hotsails. I use Fiberspars on my full quiver of HSM and I get very good shape both with sdm and rdm. If the sails would have been designed over so strange masts like told I don't think I could get the seme result using my Fiberspar, I should get very different answer when using f.e. Fire 4,5 or Smack 5,5, shaped on the Hot Rods 400 and 430.
About GPS I've never used them, I avoid cambered sails, but I know that only in 2009 they were rdm-only, now they are provided with another set of cambers for sdm masts, they tell me; and so for masts not produced from HSM...
In any case nowaday every sail brand suggest only their own masts. but on the specs of HSM sails booklet is clearly told that you can use successfully other various brands, sometime even suggesting what brands gives good answer (and so you can understand what brands don't).
This was intended like a post about sdm masts but in defence of HSM I want all to know that I've casually met HSM sails but since that time I've never found the same quality, durability, and easiness of use (also with different masts!).
Coming back to the topic, I thnk that a waveproof mast has to be stronger, so they have to build it with a thicker section. But not necessarily in reduced section, imho. So I don't know what were the reasons to change the standard. Anyhow rdm is nowaday a standard like sdm