Our truck is 3.3m high, and we definitely needed protection for our solar panels etc. A simple perimeter bar worked well for me. I made mine out of 25mm high tensile steel tube to protect the solar panels,
They are close enough so as not to cast a shadow except early in the morning.
The main branch bars are made from 40mm HT tube with a 3mm wall thickness, They protect the windscreen and the edges of the truck and deflect the branches up. We have hit numerous branches with the bars, some areas we just had to push through the small trees. We have hit a couple of larger branches at speed, one particularly large branch, (100mm) we misjudged and hit it at around 30kph, it snapped and also shattered the truck of the tree, splitting it down the middle. There was no damage to the bars except the paint, but on small dent where what was left of the branch must have spring back and dented the camper box. The key thing is to step the branch bars so that the branches rise up over the top of the truck.
Having chamfered corners on the camper box help a huge amount.
We also have two roof mounted cameras, so I can see it the branch is going to hit either side of the truck, they have been great, no more estimating / hoping or constantly stopping to check. I constantly look for overhead obstacles, becomes second nature after a while. When in doubt, I stop and slowly creep forward, and watch the branch on whichever camera required.
We carry a small lithium powered pole saw for the the larger trees or for something we know we will break off, as it is better to prune the tree than break it.
We also made some screens for the side windows, they protect them from scratches, something we should have done before our first trip, but they were essential for our trip up the Canning Stock Route, we had to push thought kilometres of tight bush lined track, the side of the truck is scratched and was stained with tree sap from all the broken branches, but the windows were fine.
This hyperlapse video shows some of the conditions we have gone through without damage to the panels or the truck. Around 2:00 min the bush gets a bit tighter, and we have to squeeze through some pretty tight areas. I have just about finished a video on the CSR, that shows the type of thing our protection has withstood.