I think Coop hit the nail on the head! It is all about flying the field. When you fly MPR at a HPR launch you don't have to worry much about recovery area. When you start pushing 75% of the waiver on HPR, you have to be concerned about recovery area and tracking. Flying the field is part of what you will learn as you move up in the HPR levels. It never hurts to take Coop's advice and start early.
Kirk is right about making thing more complicate can increase your odds of failure. But you have to consider the consequences of failing to certify, you get to fly another HPR motor. It isn't like you lose your job if the flight fails.
I think you need to have a goal for your cert flight, above and beyond certifying. In my case for my L1, I wanted to try DD, try new construction techniques, make my own nose cone, build the whole rocket from scratch, and learn as much as I could about HPR construction and flying. I did break down and buy a 38mm MMT, but everything else was scrounged or made. I then used a Loki I110 Moonburner for the cert flight so it would get the highest altitude I could. As it turned out, the flight was 4,200 ft and DD so it wasn't even pushing the boundaries at the launch site, but it was still a cool cert flight and it met the goal I had for the flight. I learned more building and flying that rocket than any other rocket I've had before or since.
My advice, worry about safety, not about failure. You're always going to have failed flights. As long as they are safe, down range and away from people, that's OK. That is why we have the safe distances for launches.
