That sounds like a real fair deal for 4500's. I get 6-9 minutes out of my IB4200's. Never ran 4500's. I think BJ has a pair and could give you more insight to them. Remeber, the higher the mah, the lon ger the run times. The longer the run times, the more heat you genrate in motors and esc's. Just a thought from my FWIW dept.

Not sure about the Piranha charger as I have no experience with them.

Yes, you should "form" new NiMh packs at 10/c charge rate or .45 amps on 4500's and "once a month" or so is what I do to "balance" them.

The 4.5 amp charge is higher than I do, though. I charge my IB4200's at 3.0 amps when using regularly. Sometimes I hit them with 4 or 5 amps while out at the lake, though. Rarely, but it depends on my time constraints and the amount of kids I bring with me and how many boats and batt packs have to keep up with.

BTW, I got over 42 mph with my SV using 12c IB4200's race packs from OFE.

P.S......

Don't go side bye side.

The way I understand it is that you can draw more amps, faster out of an "end to end" arrangement. However, the "premade" end to end packs are usually put together cheaply. The "side by side" packs you are probably looking at are of better quality. Now, that said. If you have custom packs made, or you build your own, end to end might be the way to go, but I don't think it is applicable in so far as your question here IMHO.