… Been there, done that. And with the exact board you are talking about - a 6’ HK.
I was 77kg at the time so really I needed a 5’6 or 5’8.
Basically the whole experience was ‘meh’.
I also made the same mistake with an oversized Potato.
These grovellers are designed for a certain size. By oversized you put the rails much higher in the water and mess it up. Probably a swaylocker with more experience might be able to give more info on that.
The potato was slow and horrible. Possibly the worst board I’ve ever used. The HK was not as bad. It felt ‘corky’, jittering on top of the waves and hard to control. Bottom turn it was hard to Bury the rail; id go too far or not enough.
Get a board designed for the goal. I made my own based off the HK. I put a step deck in and thinned the rails. I also lowered the rocker slightly.
Thing is, made so many mistakes building it.
But… It worked on small waves so far.
Bugger waves this weekend, God willing.
Explain situation to a shaper or get a proper egg.