Considering the amount of money already spent on equipment--not to
mention the time involved--he might have been better served by purchasing
a screen which he could have oriented in the correct plane. I don't know
what they cost on your side of the pond, but used ones are really cheap on
eBay here (seller ID: 'avforsale' has a variety every week).

He would have also gained considerably in brightness and contrast. Despite
how good it looks now, if it's merely a painted wall (excepting special
paints made for the purpose, which are available), the improvement would
have been striking.

I suspect that you are probably right, but 20 / 20 hindsight is a wonderful
thing, ain't it ?

d;~}

Arfa