I'm not aware of hard and fast rules about this sort of footprint but here are some things to consider. If you are not using holes in the PCB as alignment holes (with or without fixing screws through them) to line up with the holes in the clips then, especially if you are hand soldering them, you might be as well to makes that pads exactly as shown. That way you know when you have the clips in the correct alignment and spacing with respect to each other. However, if the pads are the same size as the clip lands then the solder will tend to bulge out like the filling in a sandwich when you squeeze it. If you add alignment holes in the PCB, even if you don't use them for mechanical fixings, you could afford to make the pads somewhere between 0.5mm to 2mm bigger all round to give yourself a nicer pad to clip solder flow profile. The down side of this is that if the holes are through plated then the solder may tend to flow away from the joint into the hole. It's easy to fix that simply be filling the holes with solder until you're sure that you have enough under the pads to make a reliable joint. Making the holes unplated stops this but may allow the joint to overheat and weaken the adhesive between the copper track to fibreglass so increasing the chances of the clips lifting the pads.

@andyfierman Thanks a lot for the elaborate and very educational answer! Will give it a thought and decide which way I will go. If I may ask though. After reading your answer I am curious about a mix of two of the suggestions... Is there any downside to make the pads say 1mm larger on all outer sides and let the area where the hole is be solid but plated (or plated 1mm in and unplated in the centre). If I have the same extra pad on all sides will the clip not align to the centre by the surface tension and I also get some extra strength from the solder around the hole?

Maybe but my experience bucket is now empty: I don't know if the surface tension will be enough to align something as big as the clip. :) Assuming that your board is actually goping to be double sided so there will be tracks and via pads on the bottom, one other possibility is to use clips with through hole pins into through plated holes but trim the pins to just less than the PCB thickness prior to assembly. Then the clips will line up but the pins won't protrude significantly (apart from a solder bump) into the underside of the board.

@andyfierman The trimming of the pins might work. Simple and easy solutions are normally the best. Thanks again for the help and insights.