My solution for the lipo cooling :
2 lipo (thickness 61mm, 210x185) into an Aluminium box , ( RS 420-2430 thickness 64mm, 250x190)
all integrated into the board with an second cover in aluminuim directely screwed on the board with Viton O ring.
it’s difficult to find an waterproof aluminuim box with this size.
The box fit perfectly in my board