Make sure your hammer bumper in the back cap lets your bolt/hammer travel back about 1/16" or more past the sear catch. I had a new one that was too long and it kept the hammer from catching without a lot of recock flow.
The alleycat sears are very hard, so I would expect any wear to be on the bottom of the hammer where it catches.
Also, the sear itself has a short slot where the mounting pin goes through. It floats back and forth. When you pull the trigger, it slips under the hammer and the pull spring can then pull it toward the back of the marker, away from the trigger catch. The sear is then free to rotate up and catch the hammer. This should let it catch regardless of what you do with the trigger. Make sure the sear is clean and has some spring action that forces (pulls) it to the rear.
If someone can verify that Puma and Alleycat hammers were different sizes, we can measure and Alleycat hammer and see if you have a problem there. The alleycat hammer diameter should be very close to that bushing size, which is around 0.870". However, I'm thinking it was actually the sear catch position that was shifted between the two. It was probably posted in here by capitalpaintball.
On your siphon tank; a possibility may be that the (tank valve/siphon setup) is restricted *snip* [I have to go with cp's idea below of insufficient opening on the front ASA.]
On a side note, I was looking at that valve chamber for devolumizing the other day. The seat for the valve body was left when they bored that space, so you can't just drop something in there to sleeve it. What might work are some nylon split ring washers with a 3/8" id that you could stuff in there in pieces. That would let the liquid come by the ports as well. However, with your front port siphon bottle problem, you may not want any less volume there.
I'll try to measure some hammers tonight. The thundercat hammer looks a whole lot like the alleycat, so now I'm curious about those two.