Thanks everyone.

Darock - you're right, its a hard wood beam mount. However, the cowling provided is pretty generous lengthwise and isn't a really tight fit. I think I can shift it around a couple of degrees with no problems, then fix and trim (if required).

Another approach would be to make another cowl. Have been meaning to try my hand at moudling a fibreglass one.

Will go fiddle around and see how much a problem I have. Thanks very much for the heads up.