PM sensors of this type (whether Honeywell or else) are not perfect. In order to be accepted as a valid reading we need at least two sensors averaged.
Is it possible to expand the current SCK2.1 to include second PM sensor and provide output PM reading as the avg between the two (or even three) sensors?
Can the SCK2.x provide additional port for additional PM sensor along with suitable averaging software in firmware?
Adding HM3301 laser dust sensor as an alternative or adjunct option might be an idea. Seeed already have them available and they have low power consumption.