Shimming vs drilling

Hi all
The guy Im chatting to regarding making my front end plusher is a retired engineer who used to do the Yamaha team mx bikes as well as pvt coms here in SA
I mentioned drilling the valves and he said he does not think its a good idea he said something about running a 5w oil and shimming or something to make the first 150mm plusher? He did my rear suspention years ago and it was fantastic.
Does this sound ok or does one need to drill those holes? Im 70kg and enjoy a plusher ride must say why did the engineers make them that size if it was as simple as increasing the the valve diameter? as you can see Im not so clued up!

Input appreciated

http://borynack.com/XR650R/xr650r_forks.htm

This page seems to cover the questions you ask far better than I will ever be able to.
I drilled my valve and it has made all the differance to me. Shimming may be better but without using the set up in the article or being a suspension guru it could take for ever to get there.

I have heard some say that progressive springs is the way to go. but there seems no real info on this for the Pig so I have assumed that this is a blind alley. If the engineer is willing to have a go at your forks then give it a go as one thing for sure there is no way they will be any worse than standard.

Hew wrote:http://borynack.com/XR650R/xr650r_forks.htm

This page seems to cover the questions you ask far better than I will ever be able to.
I drilled my valve and it has made all the differance to me. Shimming may be better but without using the set up in the article or being a suspension guru it could take for ever to get there.

I have heard some say that progressive springs is the way to go. but there seems no real info on this for the Pig so I have assumed that this is a blind alley. If the engineer is willing to have a go at your forks then give it a go as one thing for sure there is no way they will be any worse than standard.

Thanks so much for the link Hew, I told him to shim away in the meanwhile.. I should get them this afternoon will post feedback.
regards
chris