What are your plans for the cert rocket post-certification? Are you going to keep flying it at L2 power? How often?
These are questions I'm asking myself looking at L3. I don't want it to be a one-and-done.
I built my own design for both L1 and L2. The L2 rocket uses 38mm motors (I used a single use for cert). If I want to fly it and not go into orbit, I can load it with an H130 (this reload is also mailable without hazmat). I'm using it to develop my skills at dual deploy, which is required for L3. There are several Warp9 reloads in 38mm which require altimeter deployment.
Personally I have to recommend you build a L2 rocket with 54mm MMT and maybe another with 75mm MMT and fly large J, K and L motors before you attempt a L3. Part of what you learn from experience with the larger L2 motors is an appreciation for the power of the motors. K and L are really significantly more powerful than the L1 and baby J motors you can get in 38mm. Along with the experience and appreciation of the power, you learn to "fly the field". What days you can fly high and what days you need to use smaller motors and stay low.
Being an east coaster with smaller fields, I flew HobbyLine reloads, usually under 1500 ft. for my first four years back in the hobby before my L1. I flew the L1, usually under 4000 ft. for two years before my L2. I flew my L2, usually under 8000 ft. for 6 years before my L3. The only reasons I did my L3 when I did was because a kit I liked became available at a 33% discount and LDRS was coming to MDRA, only a couple hours away. I still fly mostly L2 because there are still things I want to learn and try with those size motors.
As you can see, with moving up in cert Level, an increase in how high you fly usually goes along with it. The higher you fly, the more you need to learn to fly the field. Those K and L motors in L2 will give you the experience that will be very important when you move up to the higher power of L3.
