I put a Zigbee outlet on the end of a long extension cord and positioned it at various places behind the wall but outside the cabinet. I was able to achieve a decent connection to it and it relayed signal to the one in the cabinet.
The external antenna sounds great, but the few articles I've seen about it seem very difficult to hook up and tune the antenna. Otherwise I guess I'll have to rig up a weatherproof box outside the cabinet and run the AC line to it. I don't see many weatherproof Zigbee devices anywhere.
To find the best position, I've moved the corded outlet around and seeing how it responded to a bunch of commands. Should be some kind of cheap app or device that can tell you how well a device is connected. Here is my http://hubitat.local/hub/zigbee/getChildAndRouteInfo report. I can see "Pool Light via Outlet X" referenced although I have no idea what all this data means.
Child Data:
No children
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Neighbor Table Entry
[Outlet Clothes Dryer, 01AB], LQI:46, age:3, inCost:5, outCost:5
[Attic Fan Kitchen, 025A], LQI:56, age:3, inCost:5, outCost:1
[Outdoor Bar Light, 100A], LQI:96, age:4, inCost:1, outCost:5
[Outlet Cabinet Light, 256A], LQI:98, age:3, inCost:1, outCost:5
[Light Ceiling Sue, 29CC], LQI:110, age:4, inCost:1, outCost:1
[Terry Outlet, 2E6C], LQI:134, age:3, inCost:1, outCost:5
[Outdoor Socket West Side, 363D], LQI:44, age:5, inCost:5, outCost:7
[Outdoor Balcony Lights, 4A6C], LQI:150, age:3, inCost:1, outCost:1
[Outdoor Deck Lights, 67D3], LQI:39, age:5, inCost:7, outCost:7
[Outdoor Light Garage Driveway, 8A0E], LQI:63, age:4, inCost:3, outCost:1
[Outdoor Front Porch & Yard, AF67], LQI:116, age:4, inCost:1, outCost:1
[Outlet X, B523], LQI:78, age:3, inCost:3, outCost:7
[Outlet phone cabinet (driveway relay connection), B7D8], LQI:84, age:1, inCost:1, outCost:0
[Driveway Sensor Chime @Gazebo, C00B], LQI:67, age:1, inCost:3, outCost:0
[Outlet Clothes Washer, D478], LQI:50, age:3, inCost:5, outCost:5
[Attic Fan Living Room, E6B9], LQI:40, age:3, inCost:7, outCost:3
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Route Table Entry
status:Active, age:0, routeRecordState:2, concentratorType:Low Ram, [Outdoor Bar Light, 100A] via [Outdoor Balcony Lights, 4A6C]
status:Active, age:32, routeRecordState:2, concentratorType:Low Ram, [Outdoor Gazebo, 3CAE] via [Outdoor Balcony Lights, 4A6C]
status:Active, age:64, routeRecordState:0, concentratorType:None, [Outdoor Deck Lights, 67D3] via [Outdoor Balcony Lights, 4A6C]
status:In Discovery, age:0, routeRecordState:2, concentratorType:High Ram, [Unknown, 0000] via [Outdoor Balcony Lights, 4A6C]
status:Active, age:64, routeRecordState:0, concentratorType:None, [Pool Light, 8E55] via [Outlet X, B523]
status:Active, age:64, routeRecordState:0, concentratorType:None, [Outdoor BBQ Light, BA1A] via [Outdoor Balcony Lights, 4A6C]
status:Active, age:0, routeRecordState:0, concentratorType:None, [Button4 2, BF82] via [Outdoor Balcony Lights, 4A6C]
status:Active, age:64, routeRecordState:0, concentratorType:None, [Outdoor Landscape Lights, 5784] via [Outdoor Balcony Lights, 4A6C]
status:Active, age:64, routeRecordState:0, concentratorType:None, [Outdoor Light Garage Driveway, 8A0E] via [Outdoor Light Garage Driveway, 8A0E]
status:Active, age:32, routeRecordState:2, concentratorType:Low Ram, [Outdoor Balcony Lights, 4A6C] via [Outdoor Balcony Lights, 4A6C]
status:Active, age:64, routeRecordState:0, concentratorType:None, [Outlet phone cabinet (driveway relay connection), B7D8] via [Terry Outlet, 2E6C]
status:Active, age:64, routeRecordState:0, concentratorType:None, [Outlet Clothes Dryer, 01AB] via [Outdoor Bar Light, 100A]
