Suspenders - Legend

I've had my Legend a couple of month now and really enjoying riding and tinkering with it... but one area I would like to improve on is the back lanes handling... we've got some great twisty roads in the lakes, but the the surfaces can be poor and it all ends up being a little too much for the bike. The rear end goes a bit squirrely without too much provocation, leading to a lack of trust. The front end seems ok, but I suspect that's because the rear is attention seeking at the time.
I know it's a cruiser, and I'm pushing it beyond its remit, but it feels like it wants to do better. I know a lot goes into handling, tyres are one thing I'm looking at (happy for recommendations here too)... and I will be lifting the bike and giving all the linkages a good going over etc. But I wondered what suspension changes you've made are, and whether, pound for pound, it was a worthy investment.