whats a good number for rear travel?

[59weasel]

59 SWB. some of the rodders around here tell me i need "no less than 5 inches between the rear axle and the bump stops. i will be running a 4-link (or 4 bar) of one type or another and air bags. what do you think would be a good number? this will haul butt, and thats about it. no heavy stuff, just a couple suit cases for a wknd trip most likely. i want a smooth ride not a kidney killer, but low also.