Joined: Jul 2015
Posts: 7,379
Likes: 3,221
From: NW Oregon
Bikes: 1982 Trek 930R Custom, '91 Diamondback Ascent w/ XT, XTR updates, Fuji Team Pro CF road flyer, Specialized Sirrus Gravel Convert, '09 Comencal Meta 5.5 XC, '02 Marin MBX500, '84 Gitane Criterium bike
minimum is about 2 1/2 to 3 inches on any frame type... and a bit longer for carbon frames.
and i'd say a bit extra is needed when rider weight or aggressive riding is considered.
MOST seat posts have a minimum insertion marker on the posts.
35mm simply will not be enough.... in any scenario.... and frankly, it sounds like your bike frame may be too small for you.