iphone 4 tricky, iphone 5 perfect

We use a 3d sublimation heat press from sun fly and have had varying levels of success, the time and temperature we use has varied, at the moment we are using 190 degrees for 3 minutes, the colour transfer is perfect. iPhone 5s come out perfect 99% of the time size wise but the 4s are much less successful. They fit around the sides well but length wise never seem to be short enough and the phone has about 2mm for movement.

Has anybody found this problem with the 4s and know what to do?

thanks

actually believe i may of just resolved this problem with the iPhone 4 cases. I have just put them through the press for 4 mins 15 seconds and that seems to of done the trick!!