er... there're 2 cheaper ways to do this if you really
want...
1. okay i'm not sure how the phantom's suspensions work, never took
notice, but if preload is adjustable (ask your mech), set it to the
softest, so that the shocks sag the most, i.e. the bike is lower,
but ONLY when you sit on it... this method is free... 
2. find a shop that can shave some of the seat cushioning material
for you, i.e. the seat will be a little harder (less cushion, not
so soft), but the seat height would be lower. there's a shop at
bendemeer, that does modifications of this sort. they do helmet
cushion refurbishing, plus seat rewraps, so this shouldn't be a
problem to them... this method involves some cost, but not that
much i think... expect $30 for rewrapping (cos less cushioning
foam) and a bit more for the cutting job...
sorry, cos i can't remember the shop name, only know it's at block
47 along bendemeer road, but the shop is quite obvious: first on
the right side when you turn into the carpark...
hope this helps...