SRM power meter cranks
 

So I was looking at how much this thing cost used on ebay. Ligthly entertaining idea investing in to it for next season (or maybe just saying screw it and buying a motorcycle :) ) Found some good deals, but cranks are 175mm. Is it possible to swap for other cranks like 172.5mm? Also if someone uses it with coaching or organised training program. How are results, compared just doing it with HRM?

Thanks.