It wasn’t a sip shock it was a Sebac, just a standard one and it took about a month to start bottoming. This may well have been down to the uprated SIP spring I put on.
The PK conversion costs about £150 and Grand Prix Scooters in Leicester might be able to do it. They definately have the forks in and yeh you can use a disc brake.
Failing that if you’ve a mate who can weld you just need the top of your old forks or a set of p-range ones, add 17mil to the length of the PK forks and you’re there. It’s fiddly but striaghtforward and you don’t even need to alter the steering stop as this rests on the inside of the horncasting.
A set of PK forks will cost you about £30, you’ll need a P-range(I used EFL) drum and all the bits too. Even if you don’t put a disc brake on, the handling and stopping is far superior to the Sprint set up, and you can fit a chain lock through yer forks.