Today, there is no reason to use a 530 chain on a 45-60 hp bike. Older aircooled Ducati 900s use 520 chain, and they have 75-80 rwhp stock, and up to 100 rwhp when seriously modified. Going from 530 to 520 saves weight, and possibly cost also.
The secondary gearing is a tricky issue with our XS650's, limiting the selection of alternative rear hubs/wheels, causing problems with chain rub when using longer shocks to improve handling, 18 t fronts causing shifter axle issues, and so on.
I am a bit amazed that there is so little focus on the rolling diameter of the rear wheel, as a larger rear wheel would both raise the gearing and alter the steering geometry towards less rake. A 4.00-19 has around 3.85% larger diameter and rolling circumference than a 4.00-18. Low profile tyres may have larger or smaller circumference, depending on width and ratio.
Today, I am so pissed off at myself for having my new disc brake rear wheel built with a 2.50-18 rim. I definitely should have gone for a 2.50-19 instead. I guess you all call that 20/20 hindsight.......