I installed a pair of the Brooklands Aero screens on my TD. Some things to think about; Yes, if you have a full tonnaue cover, the cover will have to altered (read- cut) IF you install the bracket/supports directly to the cowl (screwed in to the metal of the cowl humps). I have seen pictures of the brackets installed onto the face of the dash board which would not require you to cut the tonnaue cover.
In either case you should trial fit the screens with the brackets in place with either strong tape and/or whatever else (a second and possibly a third person would help) and mark on tape applied to the area to be drilled.
The considerations of where to place them is;
1. position them in the center of the cowl hump, but at the same time directly in front of you and the passenger for maximum air deflection for parctical (?) use.
2. make sure both screens are level to each other before you drill the holes other-wise they won't look "just right".
3. I installed mine on top of the cowl after reading and lookinat illistrations in one of my historical MG books about how and why they installed their aero screens on the cowl of pre-war racers.
It would assist the air flow along with the angle of the cowl up over the drivers head. I don't know if installing the bracket onto the dash would be as effective. But if you installed them on the dash you could remove the screens while leaving the brackets attached and therefore the tonnaue would fit with no altering (cutting). But then again there might be a clearance issue with your knuckles on the steering wheel if installed on the dash. It all depends what is important/works for you. They actually do block the wind if you stay directly behind them. Also my leather helmet and goggles help alot too. Your female passenger may not appricate them quite as much as you
so be prepared to put the windshield up for most passengers most of the time. By your self...... enjoy
53'TD, family owned since new
80'B