Pelt and prommy

Is it possible to mount a peltier under the prommies cooling head to achieve lower temps and would the prommy handle the extra heat?

Not feasble due to the mounting design, but more importantly it would not help you any.

yes, this is correct. if you were to get any benefit you would have to adjust the length of the capillary tube to tune the system for the new heat output. i think that if you are going to mod a phase change system, you might as well make it better, and at the cost of the materials to make a peltier cooling system, you might be able to change the refridgerant and tune the system to the new refridgerant if you were willing to do some of the work yourself.