So far it seems the problem might be solved.
Once the chips arrive, I'll have John send all my chips (including a whole load of P1 233's, enough for me to start testing them to see if they can really have their multi upped to x4) to me and I'll start doing some testing.
So far I can see 3 ways to short those 2 pins:
*Mod the cpu directly
*Do the U-wire socket mod
*Mod the underside of the socket, on the backside of the motherboard.
When using silverpaint, I might use some tape which I'll paint over when shorting the required pins, so in case of a failure I can remove the tape so it breaks the short.
I'm still unsure what this pin mod exactly does, causing the chip to increase it's multi to x4. Will the pinmod lock the multi at x4, causing the motherboard jumpers to not work anymore? What do I do with the motherboard jumpers? Remove them? Set them to x4 (Will need BF0, BF1 and BF2 for that)?