Surely 28h will be enough on 30-something mm Alu rim?
More than enough. I'm building mine 24H both ends, and I'm fat. The 20-spoke Mavic Ellipse served me well on both road and track, and that was at Calshot where the g-loading is quite a bit higher than HH :-)
Surely 28h will be enough on 30-something mm Alu rim?