Lengthening throttle cables ?

I have Honda Valkyrie bars on my 05 R3 (big improvement!) but cant lower the bars to just off the tank as the throttle cable goes tight and the revs pick up.

If you fiddle with the throttle cable adjustment at the handle bar end ,does it bugger up anything other than the free play in the cable?

Do i simply, and expensively I might add, have to buy a new throttle cable just to get an extra 25mm or so? :?

25mm is a LOT. Are your cables routed behind the triple tree? You could add some slack by routing them under the tank vice around the head stock as well.