Captain, I wish I had some good test equipment like you have described, but i have to make do with what I have and try to fill in the blanks with the RF theory that I know (thank you internet and US Navy)
DB, I know that a 1.3:1 seems like a tight tolerance before cutting back power, but the Midland 1001lwx, or at least the one that I have, seems to act as such. I had a 1001z earlier that seemed a little more forgiving, but not too much. It started cutting back at around 1.5:1 swr. I don't entirely know why, other than not having a good match causing more reflected power, but I did notice that every time the meter read higher than a 1.5:1 swr, it would not light all of the led's while transmitting. I just figured that if the signal strength meter could tell me how many watts I was receiving, it could also indicate how many watts I was transmitting, at least until it maxed out. And all of the tests that I ran indicated that the better the antenna match (swr) the more the signal strength meter would indicate while transmitting.
I know that this is a crude way of doing it, but like I said, I only consider it an indicator of antenna match. If the radio is showing full strength while transmitting, I know I'm in the ball park, but further testing is required for optimal performance. I've actually tuned an antenna like this (the everhardt, which is a 3' antenna) and have had reports that it sounded better than the 5' wilson silverload, which was tuned for best performance using traditional methods.
Figuring all of this out, knowing what I know, has been challenging, but fun. I have an extensive electrical and RF propagation background, which has helped tremendously, and I enjoy building and testing antennas and arrays. If you read the wilson 1000 base antenna thread, you will see that I have built a ground mounted vertical (102" ss whip with 32 radials 108" long) and was quite pleased with it's performace. I studies N6Lf's QEX experiments with ground planes before building it and found that my results were in line with his, which means that this stuff is repeatable. I have the pdf's from his reports if you want them. It would make a good afternoon read.