If I was to add a third R15

[Mark20]

Would I just need to change the multi-switch from a 2x4 to a a 2x6 (or 2x8)?

[Michael D'Angelo]

I don't know if there is a 2x6 so you would probably get a 2x8. D* should take care of this free of charge.

[Pink Fairy]

Yep! Although a 4x8 or 6x8 is more common - at least in my installs

[Mark20]

Right now its an 18 inch dish with a two feed LNB.

[Mertzen]

It will be a 6*8. There are no 2*8 in the HSP supply chain. And 4*8s are rare.

[jwd45244]

You can daisy chain multi-switches