for anyone wondering about two-way humidity solutions for larger areas than a boveda pack can handle - look into beads used for cigar humidors. heartfelt is one brand, the ones I use for my cigar collection are hcm cigar beads.
They work essentially the same way as boveda packets, albeit using a different medium. I keep a 28 bottle wine refrigerator at rock-solid 65% using about 8oz of HCM beads - not for weeks or months - but YEARS at a time with very little maintenance.
"maintenance" involves sitting a dish with distilled water and a new sponge in it inside the fridge for 24-48 hours. recharges the beads, good for another 6-8 months.
I don't see any reason why these couldn't be repurposed for a sealed curing cabinet of any size, just add more beads.