Hey Bob, without knowing your recipe and type of brew (extract, pm, ag) it is hard to say. The main concern would be the hop schedule. Hop utilization is affected by boil volume, which is the main concern with what you are considering. Sure, you can do it, you just need to alter you hop quantities a bit to compensate.
"I brew with a water cooler and some part from the toilet." - JohnnyO
"I do gravity feed the last gallon or two through my Therminator, but I expect you could suck start a Volkswagen before you could suck start one of these. - GilaMinumBeer
"..... Bull was right." - TXCurtis