Here are a few things I have found
Also here is a link to a mash tun calculator....just be sure to scroll down to "Can I mash it"
www.rackers.org/calcs.shtml
Hope this helps
I don't have my brewing records here with me, but I believe the MOP and myself jammed in around 46 lbs. of grain in on our Samiclaus brewday. Now that's a full mashtun for sure.
CB Don