Creating a heat map from custom data

In this case, from uplink and downlink power levels from a couple of radio sites over a coverage area.  

Doing a drive test and recording signal levels from a couple of radio towers.  For the drive test, the plan is to plop a marker in wherever we take the reading, to log the uplink and downlink signal strength along with any comments/BER/AQ/etc from the calls.  Simple, and allows us to capture everything for a specific spot.

I'd like to create a heatmap of the coverage area from this test data, which I can then use to compare with my engineering/propagation maps.  I can massage the data as needed (csv with lat,long,uprssi,downrssi,ber or whatever's needed), but how do I bring that data into a layer in caltopo?  (I have a Pro account.)