I tried putting one of your filters into the return air vent. They are slightly larger than the original Honeywell filters I currently have but I think I can make it work. It will just take an extra effort on my part to squeeze them into place.
I tried Filterbuy last year when shopping was limited due to COVID. The purchasing supply was excellent. The filters fit my system perfectly and worked GREAT! I was so happy I subscribed to automatic replacement every year!