Just got the board back from JLBPCB and whilst there is good clearance between the pins on top of the board for tracks between pins, I'm really not happy at how small the pads are on the underside of the board since these are of course one of the main ways any IC is cooled.  I tried runing a wide track through each pin but the tool sometimes removes these if they don't go anywhere. It really would be better if the top and bottom pads could be defined separately in the IC pad master.