serpentine belt & pulley problems?

replaced my stock serpentine belt today, now it just doesn't feel as tight as factory did. i have steeda underdrive pulleys, but i did not install the alt. pulley when i did the install (they are almost the same size anyway) should i have got a different belt for this application? i got the gator-back. anyone else have this problem? should i go ahead & put the steeda alt pulley on?
btw, how did gator back get that slogan? the quiet belt. um, not exactly. sounds like a vortech running in there now. thanks guys.

one other question: the steeda water pump pulley has 2 sides, one is not as deep as the other. i put the more shallow side of it facing out. is that correct? the water pump pulley is where the belt seems to be trying to come off at. seems to be tracking correctly otherwise, just kinda running close on the pump pulley, did i install it backwards? thanks.