I'm wanting to fit a brace across the back behind the rear seat so that I can replace the stock shoulder straps with 3/4 point harnesses. I want the harnesses to loop over the new brace so that they don't pull down on the shoulder.
Because its for my kids, and they have this habit of growing, I don't really want to weld it in, because in 2 years time I'll want to move it a bit higher etc.
I should add that they're already in aluminium framed high back boosters, so head protection is good.
Why do I want to go to harnesses? the existing shoulder belts have seen better days so need to be replaced anyway. The two boosters sit tight against each other, and the only way I can plug in the shoulder belts is through the back door, with a lot of difficulty. They also can't release them themselves (potentially not good in the event of an accident). Harnesses would mean they can 'do' them and 'undo' themselves (and strike me as inherently safer anyway).
So, what I'm looking for I think is some suggestions on how to fab the brace in such a way that it can be moved higher in future. What I have in mind at the moment is a horseshoe shape at the ends (over the existing vertical bars), with the brace in between. Then I'd simply drill through the horseshoe and the existing vertical bars and bolt them up. In a years time, I can move it up a couple of inches.
The potential downside I see to this is weakening the existing bars. Is that a concern on drilling 1/4" holes through?
Where might I get those horseshoes from? this is close to what I'm looking for I think
Any other ideas are very welcome.