Some little updates:
I did made a strong center alluminum CVD, 4 steel hex adaptors and I mounted original HPI baja shocks because with new huge baja wheels the other shocks were too short and does not work good.
Now the RTR weight is 7,9 kg (with 2 x zippy 3s 5000)
A video:
http://www.youtube.com/watch?v=VpGcThkc1d8
Some photos: