GainingLear:
I've done 40 through sheer gluttony, I've known people who did up to 50 a month, it just isn't a sustainable rate. Depending on how you gain expect back and knee trouble. Also expect to feel really out of shape with gains that fast.

FatAsButter:
Mmm 300lb is proper, mega fat. Committed to obesity fat. Undeniably a complete pig, stuffing it's belly tight. Treble chins and impossible clothing sizes. I'm nearly there too, it's such an erotic thought to be that fat. But I know 300 won't be enough. The women I want to look like are at least 330lb... I think my belly will pull down towards my knees at that weight and rub on my thighs when I waddle from snack to snack....

Finally Fat:
I built our bed. Had one pine board 16' x 17" x 4" thats been stored in my cellar 20 years. Flawless heartwood. I had it milled in half (16' x 18" x 4" and used just that wood to make our bed.
I built it for 800 lbs. We've been sleeping on it now for 3 yrs. As a couple we're over 600 lbs now and our bed is filling up! The frame hasn't made a sound- it's massive. Have a look-
fantasyfeeder.com/pics/photo
First stages.
fantasyfeeder.com/pics/photo
Slats in place. 1.5" sq. on 3" centers. No mattress sag.
fantasyfeeder.com/pics/photo
We've grown so fat in our bed.