I had my Frabill Trekker Max 2-man shelter on 3.25-3.75 of growing ice on New Year’s day a year or two ago. It was a small neighborhood pond and of course I didn’t want to get wet but it held.
The weather had been and was ten degrees below freezing for a week so I added those factors up and made the decision to fish.
I can’t say it was the right decision or the safest but I got on and off safely.
My nerves were pretty jumpy every time a crack would make a noise that growing ice makes. Not gonna recommend it but it did hold my portable shelter, gear, and two fishermen.