It's working fine with vanilla enemies and the included custom sprite. It's a great addition, so the player knows how much hp the sprite has.
The patch comes with very detailed documentation, so it's easy to set up.
Also it needs full SA-1 support on the sprite and the RAM address (sprites can't access to RAM in banks $7E/$7F, so you have to use a free BW-RAM/I-RAM address). I'll remove the tag until something is done about that.