vpi JMW arm lengths

Can the various VPI JMW tonearm wands be used on various bases. I know there are different lengths, such as 9". 10", 10.5" and 12, 12.5, 12.6 1nd 12.7 models. but can you substitute a 12" arm, for instance, on a 10" base? the VPI seems to use similar pivot structures, and you can buy the wands separately, so is it just a matter of putting a 12" wand on a 10" base, or are the actual pivots incompatible? Or, if its possible to do with only some bases or arms, is there a source of which are compatible?
I'm not sure but I would think it would change your spindle to pivot distance which would make proper cartridge alignment impossible
No. Even if you could merely plop any wand on a base, you'd royally screw up the P-S distance and overhang.
Yes, you can use any base and any tonearm i.e. you can use a classic base with a 12 inch arm, BUT you will need to reposition the base to the correct S2P distance for EACH arm with varying lengths.

Also, please note that some older bases have a too small of a "dogleg" that will not allow an arm with side weights to clear the vta tower.

I have seen a Classic table with a classic base and a 12.7 wand and the base has to be re-mounted to the extreme edge of the plinth. Not a good look.
Brf is technically correct. But he also confirms what I wrote.

Even assuming you are willing to move the base, it would be helpful if VPI had a kit. For example, I switched out my Classic 1 tone base for the Classic 3 base. VPI sent me a kit with the tools, jigs and templates needed to correctly position the Classic 3 tone base on the regular Classic 1 plinth. Further, they also provided me with a special platform base to cover up the hole in the plinth from the Classic 1 tone arm base.

If this is something you really want to do, call Mike at VPI and ask him if there is a kit. Otherwise, you will be going DIY all the way and you're on your own.

Been there and done it. Call VPI.

Not worth doing. I went from a 9 sig to 10,5i....if there was a difference, I really couldn't tell.
I think different generations of JMW arms sometimes use a different pivot structure. I don't think my original JMW-12 would fit on a modern base. Or at least so I've been told.
I am certainly aware that changing wand lengths will change cartridge alignment. I will be mounting on a custom plinth SP102, with an arm mount that extends and rotates, so I can change the pivot distance easily. the wands will use different cartridges. My question is more on the line of Bpoletti's post, where the question is whether there is difference in pivot structure. VPI arm wands come up fairly often in the used arena, so I want to see if my 10.5i base will accept a 12.6 wand, for instance.
Only way to know for sure is to call VPI.
When you call VPI, make sure you have the exact model of arm wand and the base(s) on which you intend to mount such arm wand.
I've owned most of VPI's 10, 10.5 and 12 inch arms. They all use the same pivot structures. There have been 2 generations of the pivot. The first generation was a cone shaped pivot which was affix to the base through a hole and a set screw. The next generation, was more of a very sharp spike and was affixed to the base with a threaded mounting collar. The older generation cone pivot can be updated to the new spike pivot for less than $100. It is a very worthwhile upgrade.