Well, i doubt we´ve to find a rule in relation to speed. For high speeds you´ll need large engines/machinery spaces and thus you stress the hull. Obviously there is a maximum of stress a hull can stand. On the other hand there is no upper limit. You can build your ships as stoudly as you want. So a 600ts vessel with a hs of 1,5 or 2,0 has no problem while one with a hs of 0,35 will be in danger.
I once again read the old thread and came up with the following problem.
When playing around with older designs, looking for chances to modify them or when designing new vessels and trying to make them fit my needs my designs "jump" between several categories of LA´s last proposal. This makes things somewhat difficult. One has to keep an eye on a designs tonnage all the time and in one second one can use x hs and minutes later a hs of y is allowed.
Maybe that´s just a problem for me because I like to play around with a designs size but if it´s not we maybe should avoid grating hs into too much.
I´d like to repeat my proposal made in that old thread:
As low as 0.5 for ships up to 4000
As low as 0.75 for ships between 4001 and up to 6000
And 1,0 for everything above 6000
Note: These are minima. A 4000ts vessel surely could have a hs of 1,00 or above making it less prone to damage by heavy weather or light ice for example.
Having only three classes will keep thing simple. Nothing is fixed of course and more classes or different categories (maybe 3500ts instead of 4000ts) could be defined. It´s just a proposal.
However, I recommend to find a solution soon because there a many designs to come and some are already building and could/should be changed if a new rule is settled down.
Ciao,
HoOmAn