I too just replaced both my older shrouds and noticed a rather large differnce in the holes on the adjuster plate. About 4 to get the same rig tension
This is not uncommon. Shroud length specs have a tendency to change slightly over the years. Also, if you bought aftermarket shrouds, they could be slightly different from the current Hobie spec. The best bet is to measure your mast rake independent of the holes in the shroud adjuster (i.e. use the main halyard or trap line to determine your mast rake).
As for actual shroud tension, somewhere between snug to slightly loose seems to be good (if those descriptions make any sense). Overtightening the shrouds is unnecessary will impede mast rotation. Having the shrouds too loose will allow the rig to flop around or in extreme cases, allow the mast to pop off the step. Otherwise, it doesn't make a perceptible difference.