Magnepan 3.6r

As you can see from my system, it's been awhile since I played with jumpers on my 3.6s. Just about anything is better than the supplied Magnepan metal, U-shaped, parts.  

If I understand what you're trying to so, I would use a short length of any brand of 12 gauge, oxygen free copper hook-up wire from Parts Connexion. Length doesn't matter and it could be solid or stranded.

I have always used the Cardas specific jumpers for the Maggies.  Probably overkill, but they seem to work and sound great!

https://www.dedicatedaudio.com/collections/cardas/products/cardas-magneplaner-tweeter-attentuator-jumper-kit-pair

https://www.dedicatedaudio.com/collections/cardas/products/cardas-magneplaner-mid-range-jumper-kit-pair

https://www.dedicatedaudio.com/collections/cardas/products/cardas-magneplaner-cross-over-jumper-kit

On 3.7 I've used solid copper and also speaker wire and didn't really see any change in sound. We're only talking a few inches here.