I'd put 16.5" shocks on. The bike turns better and is still stable I'd check YSS against the price of a rebuilt set before you decide
There is a second hand shock that works really well on DRs but I don't know if you got this military model down under. It's the Armstrong 500/Harley350 Rotax. I have a set of these on one of my DRs, they are 16.5" Ohlins, excellent quality , adjustable and the spring rate is just about right.