The new fw 3.90m33 uses the GO!messenger and Skype icon's wich fit in my 3.90m33 theme without loosing icon's,..
However i can't add 1 more icon to my 3.71m33 theme,... so i am pretty sure sony is able to allocate ram to the xmb,..

Tried to make all kind off 01-12.bmp's but you have to make sure you don't use to much ram making icon's,.. if you use infobars you can scale them down so they will be stretched,.. system_plugin.rco can be used to lower ram use,. some other rco too,.. but sysconfg_plugin.rco won't effect ram use,.. just like music_player/photo,..

example theme wich works fine with high res 01-12.bmp's is the ultimate font theme,.. ;P there are no icon's in that theme,.. or a few,.. so that's why,..