I run both the Elka Stage 4 in my Boxxer 2010, and the Stage 5 shock (bolted onto a Nicolai ION)
The stage 4 is a really nice peice of equipment, superb build and super easy to bolt in, only trouble was the o-ring around the top is really tight and no amount of slick honey was allowing it to jam into the grove! a slightdownfall is it is a fully enclosed system that is nitrogen charged so some specialist tools will be needed for servicing.
I run the "soft" in my fork as per recommendations from the ELKA guys in australia. The cartridge has some level of 'spring' in it so down grading your spring will most likely be required. The fork is super smooth, small bump sensitivity is amazing, less tuning available than the team cartridge with only rebound and low speed compression (however the high speed compression is changed depending on the cartridge you buy "Soft", "Medium", "WC"). However as the gradations between adjustments is quite small it allows you to dial in the suspension near perfectly.
These can be bolted into a Boxxer Race however you may need to knock out a pressfit spacer in the bottom of your damper leg to allow the shaft of the elka cartridge to pass through, mine went into a race so it was a very simple operation.
oh also! the 'hissing' that this suspension makes is wicked! lets you know that something is actually going on
peace