conversion to mini-split heat pump system

We have a heat pump system that functions as both A/C and heat, but traditional air-handler, not minisplit. It works quite well down to about 35 degrees. Below that, we do get the occasional “defrost” cycle, which sucks ass. We have pretty, old radiators and a gas boiler, which we left it. I rigged up the communicating stats that control the heat pump so that the “aux heat” call goes to an isolation relay, and that relay goes to the boiler. WHen the temp gets really low, the boiler gets activated. We typically don’t have much in the way of boiler use outside of Dec-Feb, and overall it has saved us a decent amount of money.