I’m not sure you are right to be jealous of the self-draining feature of the mark IV s . Only once out of four capsizes have we managed to prevent a total inversion needing rescue boat help to right the boat . They may be better inland on flat water but in waves the inversion is rapid
We’ve had similar experiences to Alan, even inland. We’ve also found inversion happens rapidly, and it then needs both helm and crew on the gunwhale to get the boat back on it’s side!
We’ve just come back from a week of family day-sailing on the western Solent from Lymington. We’ve also found that additional weight of outboard and bracket on the transom makes the boat very aft heavy, and when you sit aft to start/tend to the outboard, or even when sailing with a following tide, she will ship water through the drain tubes, so for our next cruise, we’ll be looking to find a way of temporarily plugging the tubes – if I’d wanted a wet boat, I’d have bought a Laser 2000!
That aside, it’s still a much better boat than our old MKII (non-SD)
P.S. We have sailhead buoyancy when daysailing