The very fact that HT didn't take off world wide is a strong indication that having the lightest class weight is not the most important thing when building a successful class.
I for one do not think the 18HT experience says anything about how weight is valued by owners and customers.
First of all, the 18HT's were the third lightest doublehanded sailboats on the USA market when they were launched there. The 3rd and 2nd lightest doublehanders are gone and lightest design is still is still here and growing.
Secondly, the 18HT failed for other reasons that had nothing to do with it being lightish at 135 kg. I personally think it failed for much the same reasons the Taipan 5.7 failed, its predeccesor on the US market. Combined with some specific issues related to the only HT make to ever reach the US market.
Thirdly, I know from a fact that being light weight is important enough to be a critical issue in the class grow of the F16's. If we had been 150 kg or over then we would never had gotten were we are now.
The F18 class succes wasn't hampered by it being 180 kg but that weight certainly wasn't the reason why the F18 class became succesful. Meaning when it had been 150 kg its would still have been a succes maybe even more easily so.
Wouter