We have quite a few clusters of 4 radios, each using20MHz channel widths. It works quite well. We even have a 5 radio cluster using 20x20x10. We use Cambium's OEM antenna, P/N: C030045D901A. It's listed as a 90deg antenna at 6deg roll off, and 65 deg at 3db roll off. That being said, from what I understand the new CBRS rules that are being formed will not allow for more then a 10MHz channel width. I'm really hoping that Cambium will have some carrier aggragation features in future products to get past this limitation.
I am also highly curious as to the answer to this question. We bet pretty big on the PMP450 3.65 equipment and are... "curious" about how these new CBRS rules will effect us.
There is quite a lot about the implementation of the new CBRS rules that has yet to be determined. As of right now, we don't expect the new system to be completely implented until sometime next year at the earliest.
If you're currently operating in 3.65-3.7 GHz under Part 90 rules, and you have grandfather "protected status", you'll be able to operate as you are with the same equipment until your license expires or April, 2020 at the latest.
You can read more about the rules and comments here