1. wow .. 30g in the front? what's the main difference u've found?
i've mounted 10g in the front .. err .. can't say there's an improvement of any form.
2. i've got some 2wd tire on lazer front rims too. the lazer rim fits rb5 without an issue. but being slightly wider, it means the tires will be stretched a tad more resulting in a different carcass profile.