I have sailed round hull and hard chine monos a lot in my youth and would suggest the rudder losing bite causes round up more than hull shape as the healing action is accellerated. I don't have a jib on this boat. I am very concious of keeping boat flat and rudders tightly set and very concious of the inhaul setting and trialling different settings for that.

Oh, is weather helm when the boat wants to turn INTO the wind...just kiding..

I think the boat wanting to bury is very connected to the mast rake forward. I was drag racing a H16 in 25 and it was happy and I was driving my boat with both noses underwater! Their mast has the crazy rake for that reason I am sure and I thought to rake back and put a hooter/jib on for downwind and light weather. So far it has worked well but I was just surprised by the opposite rule on my boat.