Right, so if my calculations are correct I will have a TON of extra weight left on tombpebble and nugget so I am kinda stuck on any suggestions to fill that up. Add foam to reduce impact? Cover the damn thing with titanium? Dipping the bot in shock absorbent resin?!?
As you can see, I have no clue. Any suggestions would help 
I mean, essentially yes.
I’d invest time and weight into thickening and strengthening key chassis points, like wedges or weapons supports that sort of thing, past that you can start adding in ballast for better traction or balance on a robot so it drives how you would like it to be.
Honestly so long as you’re not much below 135g I’d be inclined to leave well alone and enjoy freedom. You never know when you might need to add something!
My advice would be leave it, for three reasons:
Firstly, you don’t need to use all the weight available. People often do very well in competitions with robots that are quite a bit underweight.
Secondly, your weight calculations almost certainly aren’t correct. I don’t mean that as an insult - it is very hard to accurately calculate how much a robot will weigh. Most people either don’t bother, or allow for a large margin of error. I personally do try to calculate the exact weight my robots will be, but realistically only when I have a finished bot that I’m iterating on. It’s also an awful lot of effort, and I hate doing it. I only do it because I tend to design bots that aren’t very sensible and need the weight.
Thirdly, as Harry said, you never know when you might need to add something. You’ll find out things to improve every competition, and having weight spare means making those improvements will be way easier.
When you’ve finished the bot and got an exact weight, then maybe look at improvements if you have a lot of weight to spare. Until it’s been through a few comps I’d recommend sticking to tried and tested things, such as TPU armour panels.
Surely to calculate weight you just put the robot on a pair of scales?
No, that is just weighing the robot, and its not something you can do when you don’t have a finished robot to weigh.
Thanks everybody. Just to say that i am more worried about weight on Nugget - he is finished and 125g. But just to say, how much weight should i spend more on the chassis and protection?
Have a set of optional top (maybe bottom if invertable) panels for axes and hammersaws, maybe a weird fork thing (see US antweight Cheesecake’s sweet tooth) to beat the wedges and extra armour around the weapon motor itself to protect from big verts. It’ll be a squeeze but you can get all sorts of options to counter every threat you come across.
In my Nuts and Bots kit, I put foam padding around electronics. It seemed to work, surviving multiple roofhits and no electronic damage was sustained.
It only really added a few more grams, so you could fill the rest by adding more armour like Kraken4me suggested. Specifically you could add TPU bumpers with like 5% infill just for some air armour.
Yeah, I was thinking about what to do about hammersaws and overhead bots 
! Thanks for the suggestions guys- Nugget is getting extra 1mm poycarb armour, foam padding and a rear wedge!