EPC2204A GANFET with rectangular solder mask opening?

We wish to use EPC2204A.
We cannot do an oval pad openign in Eagle Pro pcb layout. Will rectangular solder mask opening be ok?

We design our landpatterns using rounded rectangle pads. Does Eagle have that option? E-fields is more of an issue at high voltage and high frequency. since our FETs switch fast, HF is met, however, high voltage may not be. it is still recommended to use rounded edges to minimize potential risk. Absent the ability to draw that, then proceed using rectangular features but do not reduce clearance requirements as that becomes even more important.