I am struggling to see how an increase form the stock 0.48 to 0.70 is required. I had my own (2011 990 Adv) forks resprung to 0.56 with a revalve to suit - that's an ~17% increase in spring rate and it seems fine for my 85kg 'naked' + gear + load.
On a recent trip across Australia with lots of fast and slow dirt roads (and some really gnarly sections) I am not aware of ever bottoming the forks but did use all of the suspension travel. Front and rear were set to 'max payload'; with no load this setting feels quite stiff.
I am no suspension guru so happy to defer to the experts, but my understanding was that if you are using all of your travel and not bottoming, you're pretty close to the mark. Of course, if all you are doing is riding on smooth roads than compliance may not be your primary concern, rather things like fork dive under braking, and you can get away with much stiffer and less compliant forks.
bikeless no longer! welcome home, 2011 KTM 990 Adventure!