anyone able to measure the height of the valve gear on a crossflow?

would like to see how low the rocker cover can be made.

(yea, I know I can take mine off but if if someone has a populated head lying round then saves me having to do this and possible ruining a gasket)

Pretty much no lower than it is! High lift cams can cause the rockers to touch the standard tin cover. Nothing that two gaskets can't fix if you are a bodger