To the OP: the Billrog chain set on the rears is NOT on a R4 tire and consequently your fitment will be somewhat if not totally different. If I were you, I would get what I bought for your rear tires. Aquiline MPC chains fit my R4's well, and provide excellent traction, and are a lower clearance chain than many brands/types. The issue with R4's is most chains get lost in the lugs and traction suffers. These have a bar welded into the traction area for superior grip on ice and snow. I've had mine for three years, rears only, no complaints at all. Why buy custom when these will do the job for you? Check 'em out.
Here's a link to installation and pic #5 shows the install completed on an R4 tire, with no tensioners installed, though you could add them...
http://www.chainandcable.com/cmsAdmin/uploads/TCR_MPCChainINSTALL.pdf