Warm them a little with a hairdryer (not a heatgun) get some dental floss and work that through the back slowly.
 
As long as you comfortably think you can go. Mine is on a pi kit and its lowered 48mm at the front but, still rides high at the back. Go for a good quality kit or coilovers because you do pay for what you get. What size tyres are you running ?
 
Should be ok, just check you have the right sized tyres to get the correct rolling ratio.