Heating Help

Frequent heater cycling

I have a five zone staple up radiant heat system. The zone use 7/8" under the floor staple up pex. I used heating fins and a reflective barrier also. The heat source is propane using a Polaris 130K btu condensing hot water heater (45-50 gal). I use the side ports on the system (1") and an external heat exchanger. The inlet temp to the HE is 129 and the outlet is 116, (these are averages). My Polaris seems to kick on every 5-7 minutes. This seems to frequent. My cold water inlet has a spring check valve installed.The house heat load is 80,000BTU. The house is super insulated R-28 walls--R60 ceiling (SIP Construction). The manuf told me that the Polaris will start when a 2 degree temp change occurs.
Question #1..Is the Polaris cycling to Frequent?
#2--How do I make it cycle less often?
#3- Do I need more water storage?

2 degree differential

It sound like you have plenty of mass. A 2 degree diff is very tight for radiant. as far as the floor goes you won't notice a 20 degree diff. If you are running an open system (arg) you will notice it on the dom hot water side . the solution to this would be to install a thermostatic mixing valve on the DHW outlet. and raise the boiler diff.