When you check the specs on the solenoid, check the hold force as well. The ULT will allow you to use a solenoid that requires less force when the plunger is at its far distance, but the solenoid still has to hold the on-off in place against a larger force when it is fully engaged as well. If not, the on-off will open as soon as some of the air dumps out of the chamber during a shot. The holding force is usually the largest force for a solenoid, so if the solenoid will pull the on-off from a distance, then it will probably hold it against a much larger force as well, but check to make sure. If the solenoid can't hold the on-off in, the gun will fire but you will wear out your sear in a hurry.
Except for the Automag in front, its usually the man behind the equipment that counts.