Good luck,is all I can say.If it were me I would just buy the new covers.
Here is why,I had the old 850 Fan Mate which they do not make anymore,I would open and clean the fan when needed but one day one of the wing nuts would only spin and not come off,seems that the weld that holds the stud to the base plate had failed,giving me no way to take the cover off. After talking with Maxx Air,BTW they are very responsive and helpful,they had no idea how to get the cover off.
After a lot of trial and error I managed to get the hinged side loose and pry the cover up so a small child's hand could get in and get the mounting screws loose. Now I had it loose and the plate was still attached to the cover,I took it to the bench and managed to cut the bolt off.Now I had a cover with only one mounting bracket.
I called the service line and again told the story to them,they responded by saying that they would send out a new set of mounting brackets free,which they did in record time.
But what they sent were the new Maxx Air mounting brackets with the pins,again I called and being very helpful they sent another set. The wrong ones again!
I called again and the Tech was very helpful as I explained my problem. After he looked at a picture on his computer he could see what I really needed,he explained that they had gone to a new mounting bracket with the pins and the old ones may not be in stock.
After a week they called back and said that they had found the correct parts and were shipping the last ones they could find.
They were the right ones and I installed the 850 again, but in about a month when I tried to open it I had the same problem,one wing nut would only spin. So chucked it all and went to the new Fan Mate with the pins,they will never fail,and the fan lid will open about an inch more than it did with the 850.
Sorry for the long story but I wish you luck in what ever you decide but if the wing nuts fail like mine did you may not be able to get replacement mounts. This may be why they went to the pin type of mount.
Good Luck.
2006 TIOGA 26Q CHEVY 6.0 WORKHORSE VORTECFormer El Monte RV RentalRetired Teamster Local 692Buying A Rental Class C