New 600 sx kit with wrong tail boom parts

[Isko]

Hi,i recently got a great deal on a logo 600sx. When I got to the boom portion of the build, i noticed that mikado packed the wrong boom (78+mm long),long tail pushrod and the wrong boom support rods which are not like ones on my 800 xx. They are thick wall rods and are quite heavy.
Question is:
1: do I get a longer belt and stretch it
2: cut the boom to size and maintain stock length(but i still need to get new boom support rods)

I'm setting up this 600sx with 12s.

Please give me your views and recommendations.

Thanks in advance

Isko