I think that you only need on-off control for application, not PID control.
I use my RIMS heater to heat my strike water, then reset the setpoint after I mash-in. With the SYL-2352, I Set the OUT-H at 100% dring heatup then set OUT-H to 75% to handle the mash. That way the element will never come full-on when there is wort circulating. PID is much gentler to the mash than on-off as the controller will give the element little kicks to maintain
the temperature rather than a reactive ON when the temp drops below setpoint. On-off for the HLT is fine. I have found the key to successfully maintaining mash temps, even in winter, is a thinner mash (1.5-2 qt/lb) with a couple of handfuls of rice hulls. Keeping the wort moving fairly quickly through the RIMS plenum is the key to constant temps, so don't mount your element in a 4" tube. I find 1.5" id to be perfect.