Is it possible to calculate the size from the bottom up
If you specify a hotspot for the clipNameSprite (or anything else) then that is the point in the object that is put at the position specified by the accompanying pos: clause. The default hotSpot for clipNameSprites is 0.5,0.5 - i.e the centre of the sprite.
Specifying "hotspot: 0.5, 0.0" will put the hotspot in the middle of the object's base. Do this with a clipnameSprite and all the text will be above that point (assuming that you have not rotated it).
As with any other object in the scene you can either explicitly specify a size: clause or let it take its default size. But in either case you will not know just how much of the object you will have to cut off in order to hide the name of the card - but with a bit of trial and error it should not be difficult to find something that works (but be sure to test with Duo cards as well as the more common solo performer cards)
If, for example, you find that cutting off the bottom fifth of the clipNameSprite would work you might consider using "hotspot: 0.5,0.2" to place the hotspot at the top of the part you want to obscure, you can then position the clipNameSprite at the top of (but behind) the top of whatever you use to mask it.