If those beaters are the 10kg ones, that's only 120kg of weaponry - you should probably have more than that on a HW let alone SHW.Building to weight limit and changing wheels/not wasting chassis space as TRB said will help a lot.
AI it and see if it can still beat Shebeast :P
Isn't SHW 1200 kgs?
You could probably jam some more stuff up in there. Maybe heavier weapons?
Still a bit of weight left over, maybe buff the armor or add an extra plow?How does it drive? Is it very stable? ERM was pretty stable thanks to the giant V-shaped bars on the front, but I had to make it super slow because weight limit.
It's not the most helpful angle but I'm gonna take a guess at your weapon being too far forward/your supports not going forward enough.