Should I get bigger fins for my small wave thruster?

I have a 6'2, 19.5, double winged swallow tail thruster that is designed for small waves. I've been surfing it for a couple of years now and I am quite comfortable with the board however when surfing larger faster waves I get kinda stretched out. Admittedly, this is partially because I am new to overhead waves.
My question is, would getting bigger fins help me out in steeper, faster surf? I'm a little strapped for cash and I'll probably only be surfing larger wave like 10 times a year max.
Also, if I was to get a new board for larger surf, would a regular performance thruster work better than my small wave board or should I get more of a larger 'step up' kinda board?
Really appreciate any advice.
My question is, would getting bigger fins help me out in steeper, faster surf? I'm a little strapped for cash and I'll probably only be surfing larger wave like 10 times a year max.
Also, if I was to get a new board for larger surf, would a regular performance thruster work better than my small wave board or should I get more of a larger 'step up' kinda board?
Really appreciate any advice.