Hi Johno
Great to see your latest build progress
Wouldn't worry too much about drilling the tubes for the headlight stalks, as you say, they will act as a crush tube.
Here is a picture of my build with the lights fitted.
This was taken a fair while ago, sadly not much progress since then ( Engine change & remount the Rad )
My headlamp stalks are 125mm from chassis rail to light mounting centre, as you can see, there is plenty of room for the bodywork & good clearance for the front wheels.
Those headlights of mine are like dustbin lids & are about as big as they go
Hope that helps.