I picked up a new old stock Swiss made Tropic strap from SC. I was taken aback by the cost to be honest, but then I thought an Isofrane isn't exactly cheap so give it a go!
Well it arrived the very next day and I put it on my Shogun. I think it suits the case as it isn't too thick plus the basket weave pattern looks lovely as well.
https://s6.postimg.org/bg22crng1/sss...812_174306.jpg
I did try an Isofrane but it didn't look nice at all.
https://s6.postimg.org/qt640dott/20170411_131923.jpg
The Tropic is the most comfortable rubber strap I have worn. The strap is supple, soft and wears really light on wrist. That and the light weight of the Shogun make for a great combination I think.
If you can get hold of one for a reasonable cost I would recommend you give one a try.