Different cart, much more sensitive to footsteps

Hello All; I have a VPI Scout w/JMW9 are with Dynavector DV20XH. I just changed to a Grado Ref Platinum. I also have a Phonomena phono. I was noticing the Dyn was just not smooth on vocal's and thought I would try something else. When I changed the cart, I noticed I can't even walk without skipping. I did not have this issue with the Dyn. I have the tracking @ 1.8, which is near the top of the range. I have the table on a stand, with 4 layers of MDF, spikes, then an isolation platform, then the table. Any help would be appreciated. Sounds pretty good, but I have not had enough time to play with loading, etc. Thanks!!!!
The isolation is probably not very effective if the stand itself is affected by footfalls. You could try moving the stand against a different (preferably load-bearing) wall. Or you could install a turntable shelf.

As for the arm/cart resonance being a little low like this, in my experience it's not a problem as long as your records are reasonably flat, and you can get the table isolated.
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Thanks for the responses, I will load up the floor under the table. We are currently in the middle of a renovation and I have Plenty of bricks to play with!