I also run a top mounted radiator as long as you have a decent 300gph or more pump it'll clean the air out in a day or 2, faster if you feel like picken the tower up and shaken shit around
use a small res or t fitting at the bottom, i've tried T fittings before, and bought a rez for obvious reasons, as it was stated, the T fitting does nothing to slow ater down. and if it isn't mouted at the highest possible point, it really doesn't help much at all.
in our situations the rad would be the highest, so its rather pointless i think, but it will work, barely. when that pump is OFF and the T break isn't capped. your coolant will start to come down the loop and push out of it, if it isn't held above the highest point in the system, the rad for me and you.
use a res if you can, go with a T if you can't. and dont worry about air in the rad to much. long as you use distilled water and water wetter you can wait a good year or more before you change out the watter, it should last a long time before it gets icky. long as your not doing anything bad like running a copper radiator with an aluminum block,
then again they say thats what the water wetter is for, corrosion inhibiter and all
frankly, i'd rather not take that chance with 1500dollars worth of sensitive electronics sitting under what is supposedly my 1337 cooling system.
Anyways, have a good one
My System if you give a rip