Daniel, the Minimum Seat Height is 16.5" for Frog 40" - check out our product detail page for more specs: www.readysetpedal.com/collections/bikes/products/frog-43-kids-bike
Rob, it is a long story but we can do it :) There is some tips and tricks with a chainguard. Do you really need it? ;) Sebastian from www.sklep.dzieciakiwplecaki.pl