I just replaced my (75Ah) batteries with the Mighty Max 100Ah batteries a few weeks ago (mower had about 95 hours on it and the useable capacity was no longer sufficient). For me, I had to adjust the bolts on either end of the tray, practically all of the way out, to get the new batteries to fit. There may be a small amount of additional gapping between the batteries, longways, but it wasn’t enough to make me have great concern.
I also left the rope handles on and was able to maneuver them over the battery covers and towards the outside edges of the frame that rests on top of the battery pack.
The most drastic change I made was to trim the vertical lip off of one edge of the battery covers, as they would otherwise overhang on one side of the batteries, and be sitting up on top of the other side.
Side note: The meter showed about a 50% charge level from being stuck at what it had showed before it was last charged (as they sometimes do). When I tried plugging in the charger, disconnecting it, and turning the key back on, as I’ve had to do several times in the past, it wouldn’t reset to 100%. I went ahead and replaced the batteries, fully topped them off individually, before reconnecting them in series, and then the first use or two of the mower on the new batteries resulted in zero movement on the battery meter (stayed at 50%, even after charging). It wasn’t until I used it longer and brought the meter down further that it finally reset after a charging cycle.