For those wishing to install GSX-R shocks on Ninjette, there is
no need to mangle shock by drilling out its upper bushing or your frame with hasty 1/2" drill bits by hand. The 10mm bolt used for GSX-R shock is fine because it generates sufficient friction to hold bushing in between ears.
To use factory unmolested 12mm mounting ears and 10mm shock eyelet, you just need two sleeves like this. Might need to remove 1mm from width to not extend beyond width of mounting ears on frame.
Polaris # 5135275
https://www.ebay.com/itm/302898035590