Problems problems problems (sun-spot)

I've been up on the bridge trying to get a radio signal under the floor from the nearest cable box ( next to meeting room on the other side of the bridge to the space next to the staircase.

 Basically no luck there. I can't get a radio signal under the floor (but can get over the floor) This would mean having to expose the sun boxes ( which I'm not to happy doing).  I spoke to the builder - he said there was no block under the floor ( under the door ) which you might have thought being a fire door. Perhaps he might have been wrong - I guess I must check. 

So what are the options now. 

1. Start recording rather than transmitting the data and try to retrieve the info later ( might be a good starting point but negates the interactive side of things). 

2. If there is a space under the door then run a very long USB cable from the sun-spot to a MacMini under the floor. This would solve two problems. First it would mean that the spot or aduino would get power as well as a way of sending info back. I ran the sun-spot last night and discovered that the sun-spot can basically last some of the night - I guess the radio is a power drain. I just checked and you can get 5m USB cables. This assumes you can run something under the door. Now where can I get a long stick?