I have two spare 4" pvc conduits the same length to a location I need a 800amp panel installed. The main breaker lugs only goes up to #500 mcm and has 3 lugs per phase. This rules out parallel #600mcm. Is it possible to parallel #300 mcm 3 times by using 8 conductors in one 4" and 4 conductors in the other 4". Would this cause any heat problems?