I'd like to add about 10mm to my handlebar height. I currently have 5 spacers over the headset top-cap for a total stack height of 40 mm. The manufacturer (C'dale CAAD8) says I can go up to a 55mm total stack height. Would I be OK adding 2 more 5mm spacers (I'm not sure if/how much the steerer tube may have been cut)?

Also, I already have the stem flipped up. It's the stock Cannondale Fire 3-D Forged, but I'm not sure what angle it is. Would a steeper angle stem be beter than adding two more spacers?

FWIW, I'm 5'10" and have a 56cm frame.