TKI's belt drive is available with gearing as low as 2.4:1; S3 even lower at 2.5:1, but they don't have anything for the AXYS. Both use a tensioner. I'm guessing Polaris could do likewise, but went without a tensioner for weight and don't want to sell a second version. Obviously a belt drive with tensioner adds weight over Quickdrive, but still weighs much less than the chaincase. Unless there are longevity concerns (and the reports I've read on S3 and TKI are mostly positive), I'm not sure I agree with their choice. Look at how many guys gear down their 163s and even 155s. Seems even the 163x2.6 is well outside optimum gearing, and there's a good argument to switching to a design with a tensioner (allows you to use a smaller top cog) across the line, or keeping the quickdrive on 155 and smaller and having two belt drives. Really, I'm a little surprised the belt drive hasn't spread beyond the RMK after 7 years; I suppose it costs more, but it doesn't seem durability is a real concern anymore.