G'day Bob,
It's interesting that you raise this question as I was born late enough to be taught metric at school.

But Dad always worked in imperial measurements and I started building stick and tissue, rubber powered models when I was about 8 or 9.
Most of the plans we worked from were in imperial.
As I have always had a soft spot for classic stunters I always worked in imperial and continue to do so. It just "Feels" right.

I also tinker with old cars and the only times I reach for a metric spanner is when working on my BMW motorbike (R90), In fact my metric spanner set lives under the seat as I don't use them for anything else.

So feel free to keep the plans coming in imperial measurements, Its tradition.

Cheers, Rob.