Aye tinman,
Welcome to the 'madness'!

Whilst my SRX 6 is modified, I'm still running the 'standard' carb setup, so can't help with the GPX 250 carb mod!

However, I suspect that you will have more joy when either or both SteveL and SteveH read the forum or "retired scratcher" Andy230 pokes his head in. I hope you are able to get sorted out soon. In the meantime try the 'Search' facility on the site in the top right hand of the site page, I'm sure that you are not the first person on here enquiring about this mod.
Good health.
My regards, Bill