Spring O Rama

[tx246]

ok. here is my situation. i have a very unused xt600 of the 86 vintage and have been dualsporting with those spiffy xr650r guys. my 20 yr old suspension is holding me back. i have found an easy fix for the fork but need some help in the back.
the rear shock has adjustable dampning and spring preload. i manage to overwhelm the rear at times even with the preload cranked up. i dont have a rear kicking problem at the moment.
i am headed to mexico with these crazys and would like to have some more bottoming ability because i will be carrying 20Lbs extra in gear ect. total weight me and gear should be 225-230lbs. since aftermarket springs are not common for this bike in the US, is it possible to add a collar to the spring adjuster( maybe 1/2 inch worth) to up the tension on the spring. i know im going to create coil bind at the bottom but what other effects would that have? i know this is not an ideal solution but would it help more than hurt?
thanks in advance for the replies.

[smokinrider]

got a similar year bike with the white power rear shoch and spring, seems to be just the job and i think at about £300 not bad value either

[tx246]

i agree that a new rebuildable(therefore internally adjustable valving)would be ideal but considering the value of the bike is US 1-1500 dollars a 600 dollar shock is not an option. 90% of the time, I can live with the performance as is but with the added gear(weight needed for the trip is what concerns me. I really think just a bit more pressure on the spring will be the ticket. I just dont want spring preload that will overwhelm the shock valving and poggo me over the bar.