The extra fluid reduces the temperature rise during a run, doesn't do much to dump heat. The oil touching the inner pan walls quickly cools and prevents hot oil from reaching the wall. Unlike a radiator, the fluid does not circulate, it just falls out of the internals and sits on top of the remaining oil.
Read Mackerle.
Improve it by:
1. sand blast
2. black anodize inside and out
3. if you have good nerves, weld aluminum ribs or posts to the floor and inner walls to pull heat from the hottest fluid. Examine any modern OEM aluminum pan for ideas.
4. vertical mask (16 gauge) on both sides to block header heat radiation