[wwest]

Sub-coolers rely on excess, leftover, refrigerant cooling capability downstream of the evaporator. Such capability does not exist during initial cabin cooldown of our cars as the system is struggling to reach that "target".

Once, if (BIG "F"), that "target" is reached the TXP begins throttling the level of refrigerant entering the evaporator thereby limiting the availability of downstream cooling. Even should the sub-cooler reach a point of "working" it will also raise the level of work the compressor must do.

Add a rear spoiler and mount the rear lid condenser in between.

Barring that a fender/wheelwell mounted condenser/blower combination would be my choice, with a RED DOT trinary pressure switch to protect the compressor and limit the high side pressure. Third element to control the blower.