I haven't messed with different reed material, but I have a roughly similar setup that goes a fair bit faster:
E50 polini, VM20, malossi four petal reed block, techno estoril sidebleed pipe. I'm using a CDI with no curve (powerdynamo) at 1.5mm BTDC. 18x42 gearing. On a flat road I max out at about 52 mph (about 9500 rpm); I've taken it up to 54.1 (just shy of 10k rpm) on a slight downward slope. I have a gps speedometer.
I'm currently running this setup a hair rich, so there's a little more room for performance if I was feeling froggy. (edited)