Welcome to the forum WR, for the sake of personal connection and transpariency sign off with your Cristian name as most of the hi-grade builders do. It's a small personal loosely connected club within the forum.
When guys like VMB aka Norm, or Curt, or Jerry. Wrench ? Makes good points too.
I began my Sportsman Flyer journey the last half of 2016 and know everything you don't want to do empirically.
First offering.
Just buy a built bike with your specs from Pat unless this is intended as a hobby build, whch you want to make costly mistakes. (Here I should plant my smiling face.)
Per Curt, a reworked engine from AGK is an option I chose to forgo, having a machine shop.
Last Spring seeking more power from my 79cc Predi, I did the full AGK treatment.
Port, polish, .050" head deck, heavy valve springs, remove governor, and ARC billet flywheel.
Everything else is pretty much stock Flyer from Pat.
At present, I have not proved out my latest carb adjustments. Now you are on board I better get back to work.
Some threads of mine that may be of interest.
(1) 79cc Sportsman Flyer build | Motorized Bicycle Engine Kit Forum (motorbicycling.com)
(1) Bike builders that have machine tools/shops | Motorized Bicycle Engine Kit Forum (motorbicycling.com)
Best regards,
Tom