I was thinking about splicing wires from the ESC main battery feed before it hits the ESC, with a servo wire with a male end and plugging it into the one of the empty channels on the RX,,, I would also cut the red wire from ESC that provides power to the RX since its only 6 volts.
I have a 2s 7.4 volt - 5000mah - 40c lipo battery.
Tekin Redline 8.5 with RS-Pro.
Would this wreck my receiver, can it handle the power ? ? KoPropo 409s RX
Would this draw power away from motor and make it cog or cut out when I turn the wheel.
I am looking for the extra speed and torque that can be obtained from 7.4 volts.

just get a faster more powerful servo, probably a lot cheaper in case you do destroy the ESC.

I was thinking more like
for 6 volt = JR DS-8717 or DS-8711
7,4 volt = JR DS-8717HV or DS-8711

for 1/8 buggy Hitec 7955 or JR DS-8711

I fly airplanes, big airplanes,, and that is where you can really tell a quality servo,,,, JR and Futaba are unmatched in gear mesh for smoothness and performance and zero out perfect everytime...
Im new to the RC short course racing, and looking for all the info I can find on the different products.
I looked at Savox and KoPropo,, those looked like good servos, and had some good numbers.
Im guessing that the ESC's from the manufacturers will be onverting to 7.4, since the servos companies are all making them.
too bad I just built 3 trucks with the RS-Pro and Havoc Pro ESC's,, they will probably be out teched by the end of the year.
to your advice of get 6 volts, probably good, LOL,,, I got both the JR DS-8711 & 8717,,,, (6-volts)

Dont think the ESC manufacturers will be in a hurry to make internal bec's operate at 7.4v

Most of them are struggling to get them to function at 6v

If you want to run a HV servo you really have 2 options at the moment

1. Run an external bec at 7.4v straight to your RX (assuming it cant handle the voltage)

2. Run an external bec straight to your servo (will require the signal wire from the RX) and use your internal bec to power the RX

Cheers