For a 100cc it might have been a better fit...

I assume you're looking to fit blisters to the cowl sides to cover the plug boots...

Perhaps you could find a couple small wheel pants and cut them up to make something that looks nice?

The the outline of the "blister" could be traced onto the covered wooden cowl and set in and epoxied... maybe even glassed from the inside to really attach them firmly.
Of course they could be carved from balsa too... just maybe a little narder to cover or paint...