Anyone knows a a manga that the uke is much taller than the seme?

Dog style?!

koitomo

MIght not be on your taste, I dunno, here:

http://www.mangago.me/read-manga/me_o_tojite_3_byou/

http://www.mangago.me/read-manga/hakidame_to_tsuru/

http://www.mangago.me/read-manga/eien_ni_owaranai/

http://www.mangago.me/read-manga/bokura_ga_koi_wo_ushinau_riyuu/

http://www.mangago.me/read-manga/the_science_room/

If you want more you could see on this, although the tag is "younger seme".

http://www.mangago.me/people/tag/132147/younger+seme/

Oh and if you feel like reading crossdressing yaoi, here's one "Oh, Sammy!" (if you've not read it yet)

http://www.mangago.me/read-manga/oh_sammy/

Thank you so much!! Gladly I'm going to devore all them ლ(´ڡ`ლ)

GLad to be of help.