Pro-ject arm on Rega Planar 2

I have an old (NAD branded) Rega Planar 2 turntable with no arm (I transferred it to a Michell turntable) and I was wondering if anyone has had any success mounting a Pro-ject arm such as one of those here https://www.analogueseduction.net/tonearms/pro-ject-replacement-tonearms-spare-parts.html on a Rega plinth? (They are so much cheaper than Rega arms, and the plinth would require surgery anyway due to the Rega mount having changed, and even a second hand RB250 looks expensive, even for fairly beaten up examples.)

I understand the crucial thing is arm effective length and that Pro-ject arms have a longer effective length than Rega arms, so one question I have for anyone who has attempted this is about whether the overhang at the counterweight end might move beyond the boundary of the plinth while playing, making it impossible to close the lid?

Also, in general, how easy is it to find the proper measurements for mounting, and any other things I should look out for?

Thanks.
 
It would be wise to compare the spec for overall length, effective arm length and mounting hole diameter. The rega specs are on their website, and in a similar manner if you go to the project webpage for that particular turntable i would imagine that they too publish the arm specification.

If that fails checking the images and dimensions of the planer 2 wrt to the project donor should let you scale to understand if the counterweight would over hang, If both plinths are in fact the same dimension things should be relatively safe for a quick fix. The height of the arm may be one to watch and also the height of the rega platter compared with that of the the project.

Maybe analogue seduction could help if you email them your question.
 
The new arm should come with a mounting template. If not, don't buy it.

It may be necessary to mount the new arm in a different location on the base than the original arm,
in order to get it to fit under the dust cover properly, regardless of the effective arm length.