measuring to lower a vehicle

what up, I just put my 24x10 intro rockman wheels on my 2005 chevy xcab, but now when it comes to lowering the truck, i cant figure out how low to go. if i measure from the fender to the top of the tire, the front gap has 4.5" and the rear has 5.5" of gap.
 
does that mean I can get away with a 3/5 or 4/6 drop and be ok for daily freeway and city driving? 
 
any help is much appreciated.

 
i would post picks but i dont know how. 

how far up can they go before they hit any of the body? fender lip, wheel well tops, ect. id say if they wont tuck, leave a couple inches to the fender. or if its close, you can roll the lips and go just shy of dead even. if you are able to tuck, you should be fine. up front. take your measurements with the wheels turned to lock also. that will show other clearances. i know on my yota, i dropped it like 7" all the way around and had to hammer the inner fender pinch welds over flat, and form the tops up higher. and roll the hell out of the lips. rear is stock.

what size tires r u runnin. that has a little bit 2 do with it. but if were my truck i would do a 3/5 on 24's