The only good solution is going to be to get a run of new rear housings made somewhere. Original parts would have to be 3D scanned and a big investment would have to made for injection molds, but I think there’s enough frustrated 1400 owners out there to be worth it.
@maceffects would be the best bet for this but I think he said something about why he’s not doing it? Don’t remember.
As for the shim, ABS will probably help, but probably not enough? I opened up my Latitude CPi (same hinge issue) yesterday and found that they did almost everything right. Mainly, they had metal pieces in there that extend up the left and right of he display housing to remove stress from that area. Despite this, it’s still cracking. I think they put the standoffs too low down, but if a metal support piece on each side isn’t enough for the brittle plastic, will a plastic one even be as good as that? Plastic flexes. As for the CPi, I actually found a source for NOS rear display housings (and I may have bought 5 of them - what can I say, I love the CPi) but I doubt anything like that will be found for the 1400.