Bonjour Dennis,
Happy to see your progress. You have not yet installed any segment on your pistons. How do you plan to ensure their tightness ?
Viton O'rings? Old-fashioned cotton braid? Micro grooves? On one of my D10, my friend Max made pistons with Teflon cups (coupons à coupelles de Teflon) :
http://www.vapeuretmodelesavapeur.com/accueil/index.html (search "piston").