You shouldn't need to resort to filler/bridging strips
As Talonmotorsport has posted.
Crush the end of a spare MIG shroud to give it a flat slimline profile. as said make sure that the shroud does not make contact with the tip.
Shrouds are easy to flatten as they are made from copper .
You may need to reduce the length of the shroud a little, you will be looking to have at least 5mm of tip showing past the shroud.
You will then need to up the welding current, Gas & perhaps the wire speed a little.
On a 150amp set, full power.
Set the wire speed so as when you stop welding there is abot 5mm of wire showing.
The next important thing is going to be the technique you use to weld the joints.
By far the easiest method is Vertical down.
Make shure the joint is vertical & weld from top to bottom. Manipulating the weld pool as you go.
On the very accute angles, you may find that you can only get to the half way point.
Stop, flip the chassis over, then complete the weld.
On a personal note, I found no angles on the cassis that were not possible to get to.