Lowest static drop for towing?

[fishmunger]

Hey guys, I have my 64 short fleet lowered 4 up front and 5 out back right now. I'm using it tow my boat ~350 lbs tongue weight. I've c-notched it and relocated the shocks, it works really good. I was wondering if anyone thinks 7" rear drop will still work? I don't want bags, it's my DD and I don't have the money anyway, I don't want to run bags with schrader valves either. So would 5" springs and 2" blocks be ok, or would I be better off to stick with what I got now (3" springs, 2" blocks)?

thanks,

Nate