Hi Matt,
Yes, 300g would be easily attainable if I used the 0.2oz veil on the outside.
The 0.3oz will take quite a lot extra to fill to a 'paint ready' surface. So I will pay a weight penalty for using this.
However for these particular wings , with the low % tip sections, I think it will be worth the penalty. I have had flexing wing tips on a bipe already (due to some strut issues) and it is difficult to handle, especially in turbulent conditions.
Also as the surface is so hard and stiff I don't think the honeycomb pattern will show through very much if at all !?? Maybe use smaller cut-outs with the 0.2oz.

Brian