They're spendy, but a kako (however you spell it) throttle lock is money well spent which will allow you to shake out that throttle arm to get the tingles out of your fingers here and there.
I bought the '03 640A after I had spent two years reading up on them. I had never even ridden one of these bikes and had never even seen a 640A in real life before I bought the bike. They're huge. I was expecting the vibes I kept hearing about, but I didn't expect the bike to walk across the shop floor while it idled on the center stand. Holy F###@@@K were the two words than I kept muttering on the 20 minute ride home from the shipping company. I was seriously worried about the vibes, dealing with the vibes, the numb fingers.
It's a freaking mean vibrating beast, the 640A is, but that's why we love them.
You're gonna grin your fool head off every time you ride that bike of yours. You'll get used to it, it'll get used to you.