If these 'tartan police' are truly ignorant you may get grief about the saffron kilt (if that affects your decisions). I personally would still ditch the fly plaid, just think they are a step too far for my tastes, take that money and invest it in other accessories.

Having your own PC is great, I'm sure it will look smashing. Remember while stillwaters are popular they are not 'made to measure' like a USA Kilt or the like is.

I would say I would go with what you feel comfortable with, you only get one Prom (I think!).

Good luck!

Andy