Turntables That Can Accommodate Longer Tonearms

For longer tonearm you need bigger plinth, look here
What plinth do you have for your SP-25? Change the plinth, not turntable. You can completely remove the dustcover. This is SP-25 with "12inch Jelco for example. 

Thanks for your reply,  I currently have a standard SH-15B2 plinth with a custom-made armboard for the 270mm distance, and it works great...but the overall fit under the dustcover is very tight.  I might have to settle for using a non-standard dustcover with this combination.

I wanted a long arm, then I learned here how playing mono LP’s with a true mono cartridge sounds better (definitely does, degree of improvement varies from a little to definitely a lot).

so, I found a JVC CL-P2 Plinth with 2 removable arm-boards, I fit a 12.5" stereo arm, a 9" mono arm, pre-aligned, instantly switch during a listening session; then I found a very compact arm and squeezed a 3rd arm on that plinth, MC Stereo; MM Stereo; MM Mono, they just fit under the big dust-cover.

You need to consider how to switch inputs into your preamp; I found a SUT with 3 front selectable inputs, 4 optional MC loads/x-factors, and importantly MM Pass. Fidelity Research FRT-4. 3 in, rotate switch, one SUT output to preamp MM Phono.

3 arm TT is shown in my system photos here:

https://systems.audiogon.com/systems/9511

JVC DD: TT 61, 71. 81 (mine) all fit that Plinth. The plinth is a 7 layer composite with real wood veneer.

Someone steals it, I do it again without considering anything else.

That looks good, Elliott, thanks for sharing.

It looked better before I squeezed the 3rd arm on. I gained the functionality, but ....

wanting fixed cartridge on the long arm made changing headshells on the rear arm more important, thus the 3rd arm for Mono to go.