Yes you will notice a difference in the height if you put a 90 on the front. The 90 you have on the back has raised the rear about 1 inch from stock. If you go back with an 80 in the back it will lower the bike back to stock and may give your feet a little bit better reach to the ground.
Pirelli makes the
Diablo Scooter tire in the stock size for the pre-gen. I have them on my bike and they have very good grip.
Stock front size: 100/80-16
http://www.denniskirk.com/jsp/tpl/ti...fCatId=&mmyId=
Stock rear size: 130/80-16
http://www.denniskirk.com/jsp/tpl/ti...fCatId=&mmyId=