I'm designing a CMOS H-bridge single sided board. To keep it small as possible, I would like to not connect the transistor's drain by trace. In spite off, as they are connected to the mounting base and I will be using heatsink, I would like to know if this connection is enough. This doesn't sound a good design to me, but since it's a low current application (2A, with 4A peak), I think there will be no much problem (actually, the heatsinks are not even mandatory, since them are almost at room temperature).

The question is, how bad is this practice? Should I really avoid it at any costs or are there specific cases that I'm allowed to do this?