Lots of great knives out there to do the job. I'm sure Brad can help you find something that matches your criteria. Like Brad said, you could spend $1,000 on a knife but it is useless if it isn't kept sharp. If that is an issue for you, you might look at the Havalon knives like the Piranta...
I bought one of these from Alan to put on my 458 Socom. Love mine. The big objective sucks in the light at sunrise and sunset. I think it is a great value for what they cost.
If you decide to take open up the ejection port with a file, be careful that you don't remove too much from the top. As you mentioned, the detent on the cover will not engage to stay closed if you remove too much material. You should be able to find drawings and specs with a quick google...
I like the Lancer mags. I'm not sure what WC "modifies" on these. Maybe a center follower? I have never had an issue with mine, unmodified 20rds. I don't personally see a need for the center follower. The feed lips should center the round just fine. I have only run ballistic tip, so I don't...
Dixon zero-turn mower with 42" deck. Runs great. Starts right up. Oil change and sharp blades this spring. Only selling because I am getting a newer mower. Replaced main belt to mower deck in the last year or two. Replaced battery last spring I believe. Have a couple extra sets of blades...