Mounting Amplifier to Subwoofer Box?

Ok, I know it's not ideal to mount an amplifier to a subwoofer enclosure but, I don't have the space to sacrifice mounting it anywhere else. My subwoofer is a DXI112 from Polk Audio and the box is made very well out of 3/4 mdf and braced. Do you think I will have any problem with vibration mounting an Alpine MRP-M500 to the box? I have had smaller amps mounted to boxes before with no problem but I don't want to kill my new amp. Should I mount it to the sloped back or the Side of the box?