Welcome Barry!
Trad Mog suspension is 'firm'. You will certainly find it stiffer than any Volvo road car (and probably that of a race car). If you have standard springs you will very likely have 'falling rate' suspension.
Both the Rutherford set-up and soon to be new factory suspension should be rising rate. One of the easiest ways to reduce the present falling rate set up is to fit shorter main springs, so allowing a little clearance between the rebound spring and the sliding axle. When you check your suspension later I bet you will find neither spring has any clearance, thus the spring rates are additive until the main sprin is compressed sufficiently to clear the rebound spring, when the main spring rate is the only one that applies.
Ask for a chap by the name of Peter Ballard on MogTalk - he will happily explain it correctly, with as much maths as you can handle, should you so wish.
But as Frank says - drive the car for a bit before changing anything - and enjoy it!
Cheers,
