Matching a Mazzoni Stealth Ant?

Bottom line: I like the loop -- a lot. Using 50 watts, I've been logging +6000 mile "QSO's" via FT8 -- Trans-US/Canada, SA, and trans-Atlantic including the EU, Ukraine, Russia, etc. No SW Asia, Australia, or new Zealand yet. The plane of the loop is oriented E-W but the azimuths I log are all over the compass.

I usually follow the grey line, starting on 17m at about 1600 edt and work my way down to 40m by 2200 edt.

In short, the coax from the loop is connected to it's tuner at the OP atop the Flex. A 3 foot length of RG8X connects the loop tuner to ANT2 on the Flex.

For photo's of the set-up and links to Mazzoni info see: https://www.qrz.com/db/KE2KQ 

I get a pretty repeatable <1.5 VSWR on 40 thru 10 (as measured on the Flex) by:

(1) Auto-tuning the loop.The loop's tuning is initiated by it's own USB connected keypad. Step (1) almost always gets between 1.2 and 2.5 (as measured on loop's auto-tuner). I can see the loop tuner's carrier at work on the Flex pan display. I ends up right where it should.

But then I have to (2) auto-tune the Flex. When the Flex ATU is bypassed it measures an off-the meter VSWR. So it pulls my tx power down to nothing to protect itself. 

Often I have to iterate on (2) several times and get either very high or <1.5 VSWR (as measured on the Flex). It's like rolling dice! :-) But eventually I get to a very low VSWR.

I'm using a new, continuous, 50 ft run of RG-8X made up by DX Engineering connecting the loop with it's tuner (which is sitting atop the Flex). The coax and loop tuner control pair are just laying on the lawn. The coax exits the tuner at right angle to the plane of the loop.

I'm learning how to use Flex's 'profiles' to try and capture all it's many settings in one place hoping that will eliminate the hit or miss part with the Flex ATU. No joy with that so far. The Flex ATU memory is on.

What's a Flex'er to do?

73,
Tom KE2KQ