[Akami]

Edgi nemo kit would solve your problems, including the undervolumed matter. I don't really know any other good upgrade kit for striker series out there. Maybe try escw piston and spring guide, which is a standard size so you wouldn't have to replace the cylinder at the cost of still low air volume : Set Piston & Spring Guide For Ares Striker As-01 E.s.c.w. Fps

For the sear, isn't AST comes with 90° already? I couldn't find any sear upgrade other than from Airsoftpro. You might try it, but I couldn't find any review of it yet as for now.

 

[Akami]

They do, but I heard mainly bad review about it. Cylinder tail not welded properly, cracks in the weld, etc. It's also sold everywhere where I could find it. Wonder is Ares working on something to improve it or something else. Been a while since they made something for a bolt action springer.