Yea that connector will do fine for running 2x 3s lipos to make 6s,

Honestly herr I hated soldering until I bought the right iron,

I had tried multiple irons from 60w up to 100w,

None of them were getting near the heat required to solder esc and lipo battery wires,

Then I bought a cheapo Chinese 200w iron on eBay and now soldering is seriously easy,

The only issue I used to have with soldering was not enough heat,

I can now solder 8awg on lipo packs within 5 mins,

6s will be nuts power, but perhaps in a Truggy with a centre diff it would tame it a little,

On a monster truck with no centre diff 4s is plenty and not too hard on the drivetrain