If I have a tank that holds the sheets of film like a toastrack should I agitate the same as one would with a spiral tank for 35mm?
Then I would agitate for 30secs initially to loosen any air bubbles, then 15sec every minute. By this I mean a very quick inversion of the tank.
Not sure if thats appropriate here, it depends on the seal on the lid.

Here's what I do. I load the film into the tank's rack in the dark....and insert it very quickly into the tank, pre-filled with developer. I vigorously slosh the rack up and down to remove air bubbles...put the lid on...turn the light on...and then agitate with a circular and rocking motion 15 seconds every minute. Since the tank would spill the chemicals if inverted, of course I don't do that. As for development time, I include 15 seconds for the initial "sloshing"..and 15 seconds for pouring the developer out, in the total time. I then put the tank under running water for a couple of minutes or so...empty it...and pour in the fixer. I fix for 7 or 8 minutes...remove the lid...make sure the negs are totally clear...pour out the fixer...and wash under running water for 7 or 8 minutes. (Some people use hypo clearing agent). I then pour out the water...pour in a wetting agent solution...remove after a couple of minutes...shake off the excess...and let the negs dry. If I'm in a hurry, I remove the negs and squeegee them off. Fred.