Is the at 150mlx a bad match on the jmw9 tonearm

Effective mass of the JWM 9 is 7.7g. The AT150MLX weighs 8.3g and the mounting hardware add 0.5g for a total effective mass of 16.5g. AT150MLX dynamic compliance is 10. If you run those figures through the resonance frequency calculator, you get a resonance frequency of 12.29 Hz, which is at the upper end of the 8-12 Hz recommended frequency range. If you can see the woofers pumping, that may be a damping issue of some sort, the kind moderated by a fluid-damped tonearm.

You can also lower the resonance frequency into the 10's by adding headshell weights to bring effective mass up to around 20-25 Hz.

What doesn't look right to me is flexistand? Don't know what that is, but VPI's don't like flex. You're right with the other stuff...a solid connection to Earth. I would take it off the flex stand and see what happens.. Also damping may cure this. Add just 1 drop at a time and listen. If the sound becomes soggy...take out one drop with a Qtip and try again.

Zd542 My phono pretty is am Avid Pulsus and is set to 47000 k ohoms and a capacitance of 100pf.
Johnnyb53 I am not sure that I want to add a headshell weight. It sounds like you are saying adding a weight of about 13 to 18 grams.that seem like an awful lot of weight to add.
Stringreen unfortunately I don't believe the damping is an option on this arm.I am not sure the stand is the problem but I am going to try moving the table and see what happens.I think there are some pics of the stand in my system page although most everything else has changed. The stand its self is near 150 pounds and not as flexy as the name would give the impression.
I am kind of starting to think it is just not a good match to the arm. I thought I saw a few threads of folks with it on the same arm but I could be wrong

A low mass arm and a low compliance cartridge is not a good match. That is the reason why you did not have woofer pumping with the higher compliant Ortofon. Return the cartridge for one with a higher compliance or you will have woofer pumping until the cows come home!

Wilson...it looks like they have changed the arm since you got your table...the new ones can be damped...they come with a bottle of damping fluid. Also...I know this is an anathema, but try no anti-skate. Makes the cartridge sound better to my ears.