6 gallon batch - How much boil volume?

I have been upscaling my extract recipes to 6 gallons. I do a full boil, and beersmith recommends 7.5 gallons for a one hour boil.

I get very nervous boling more than 7 gallons in my turkey fryer. It is very close to the top of the pot, so I get worried about boil overs. Plus, the added weight makes moving the pot with stability more of a chore.

Is there any harm in boiling a lesser amount, like 6 to 6.5 gallons, then adding 1 to 1.5 gallons of bottled water at the end of the process just prior to the yeast? Will a little bit less boil volume have that much effect on the bittering hops?

Extract brewing right? No, there's no harm in topping up a few gallons.

Boil 5 and top off after cooling with filtered tap water.

Or splitting your boil. I did that before I got a larger pot. 5-5.5 gallons in the turkey fryer, the rest on the stove top. I would mix it all up before splitting, just to assure even gravity. Also, adjust your hops for a 5.5 gallon boil.

I think even at 6 or 6.5 gallons you'll still have a lot of volume and get some good hop utilization. I'd go for it as almost every extract batch I've done or tasted was topped up and they all came out fine.

Thanks for all the replys. The hops utilization is my biggest concern, but it sounds like it's not that much concern.