Hi Ron
I've built Gary's cutter 'Flyer'. The plans were accurate and easy to follow with very few errors. I enjoyed the build and the finished model sails well and looks great on the lake.
Downsides: It is big, has to be assembled at the side of the lake as I can't transport it assembled, and it goes best with a strong breeze.
I know that Gary advises against scaling his designs down. 10% may be OK, but reducing it to half scale would introduce a lot of design issues relating to weight, sail area etc.
There is a blog of my build here:
https://model-boats.com/blogs/86653