Custom Wilbers Rear Shock for Prolink

[swarrans]

I've pretty much decided to upgrade my air-leaking 82 Prolink rear shock after going out today with a pillion passenger and the rear feeling like it was bottoming out - I'm about 75Kg and my wife is 50Kg so we're not exactly obese!
The Wilbers shock I have in mind is custom built for one's weight and they can also build it to a custom length - the trouble is they say they haven't ever done a custom length on a Prolink so I need some guidance.
1. I have an 80 profile tyre ilo the standard 90 so getting it on it's stand is hard work - what I'd like to do is increase the length of the shock to give me about 10mm more ride height at the rear wheel - does anyone know what the "ratio" between shock displacement and rear wheel travel is? - ie if I want 10mm at the wheel how much longer should I ask them to make the shock?
2. They say the standard prolink shock is 288mm long - can anyone confirm this so I can do a sanity check?
3. Do you think it will be OK to increase the shock length a modest amount linkage-wise? I would have thought it will only take about 3-4mm increase in length so I wouldn't have thought the linkage would cause any problems.

Many thanks in advance

Simon

[patzx12]

Wilburs will know the ratio. just tell them what you want and let them sort it.
I got a shock made to compensate for the change from 18 to 17 rear wheel

[swarrans]

Many thanks for the reply. The email response i had from Wilbers said they didn't know the ratio and they said they had never lengthened a CBX Prolink shock - but it sounds like they have at least done yours!
How did yours work out are you happy with it?

Regards

Simon