You can do that but you will probably only get2 or 3 15 min flights before needingto recharge. No matter what, you'd have to keep track of your voltage after every flight andrecharge when you read around 7.4-7.5 volts on your pack. Never drive a 2S Lipo to less than about 7.2-7.3 volts. You will have a time getting a charge back in it (chargers will not drive a battery too depleted), and the battery may be damaged......

You may want to go with a 4000 ma 2S LiPo, regulated to5.7 volts. You should be able to drive the dozen servos and ignition for about 5 flights 15 minutes each. I suggest you take a good look at and buy the Tech Aero IBEC for your ignition battery eliminator circuit. It has all the RFI filtering built in. Again, make sure to check voltage every couple flights until you are certain how the battery drops and how the drop repeats over many flights. Actually this is a good practice to get into across the board but especially for the more complex airborne set-ups. I use a small digital volt meter to keep track

In regard to the FutabaTech telling you to use nicads, some Futaba servos get jittery when driven at higher than 6 volts, and it may be that the servos quoted are some that do. I don't fly Futaba so I can help in telling which servos will or won't. The Futaba tech was in the best position to make the call.

However, althougth standard 4.8 V nicads at 4000-5000 ma capacity will work okay, they will be very heavy (basically 4 size D cells in series,about a pound) and use up lots of space. Even 4.8 V NiMH battery of similar capacity will be heavy. LiPO will be much lighter.

You have some choices. As far as V-Regs, Tech Aero has some of the best around....Look up their stuff on-line