[Patrick]

You will have to use an external bec and disable the internal one, it's not really on option on 4s.
It doesn't involve any cutting though.
The bec input wires just get soldered to the esc input wires. And the output plug goes in the battery slot of the receiver.
And to disable the internal one there is a small three wire lead (black wire, red wire, yellow wire) that goes from the esc and gets plugged into the receiver. To disable the bec all you have to do is go to the plug at the end of the lead, get a small pointy object and lift up the tab on the plug that's inline with the red wire. You can then just slide the red wire out. Tape or heatshrink it back out of the way and it's done. Once you get the stuff and have a look at it, it will seem really easy.

I like my quark. I did burnt out 2 of them early last year when I was using a 7xl on 14 cells nimh in the middle of summer, but both were replaced under warranty. My third one has been mainly used with a 1515 2.5D (1700kv) in a truggy and e-maxx on 5s for racing and some high speed bashing. I also use it on 6s sometimes as well for bashing and about 15 minutes of practice laps on the track. I'd like to know how many people have actually used quarks on 6s and how many worked and how many didn't, because this one has never even blinked when I've used it of 6s.
About a week ago I used it for 10 minutes or so on 6s geared for around 55mph no problems. It's summer here now and it's been used on some 40C+ days (104f), but I haven't thermalled this quark.
I've always used them with the rcm heatsink and 1 40mm fan, but I think the neu has helped a lot to keep this one working for the last 7 months. I haven't done the internal mod or put extra caps on it.
If you don't go crazy on the gearing I think yours should be ok with the neu, heatsink, and 2 fans in a buggy, but if it's not, they'll replace it.