Having used my HM for about 5 years without a damper and building a damper last year, I would say go with the damper. The temps are much more stable with the damper. I built and printed an adapt-a-damper and love it!
Wbegg sold me assembled damper for less than i could have printed it , bought parts, and put it together for. Look into this.
I bought heatermeter from bryan. Reasonable premium
about $50 for it to be put together for you and tested, imo. Would take me many hrs to do it, if not days to troubleshoot a mistake..... My time is worth more than $10/hr to me.