Progressive Fork Springs for a noob

[nategs550]

Ok this is my first dive into messing with suspension and have decided to get progressive springs for my GS550. Ive emptied the fork oil, removed the dual springs that were in mine. Fork oil level and the spacer are my concern. Should I just fill it up until it reaches 140mm from the top which is the maximum amount according to the chart? Also, my new springs call for a 162mm spacer to match the length of the stockers, 150mm to be flush with the top of the fork tube. Is this extreme? The springs are for a '80 gs550 but there's always a possibility my forks aren't stock which would then piss me off.

 

[xb33bsa]

just to be clear,the measurement from the top with the oil level is with the forks FULLY compressed after they have been stroked a few times,to make sure they are all full no air cavities
you can vary this level up or down slightly less air space makes the air-spring effect more progressive
as far as the springs you may need to experiment with preload until you get the desired ride height/sag with you on the bike seated normally if it turns out you need a ton of preload then the springs are too soft
are they actually progressive wound or is that just the brand ?
there is a whole lot more to fork tooning than what i just laid out but that will get you started for test riding