Here is how I did my batt hold down mod:
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ORIGINAL: Silentbob343
Here is my setup to hold the 25mm tall batt
Two 6-32 threaded 1" tall spacers .25" OD
Two 30mm long pieces of 6-32 rod secured via red loctite
Two 6-32 coutersunk screws
Two 6-32 Wingnuts-I like the nylon ones, but they are a bit big and hit the antenna post when it gets close to being snug.
To get the spacers in the post holes you will need to get a .25" drill bit to enlarge them. I recommend you grind the end off the bit to allow it to travel to the bottom of the post hole. The chassis screw holes will also need to be made slightly larger to take the 6-32 screws. The previous owner of my MQ had already screwed holes in the chassis so I had no problem making a few more changes.
I also ordered some 4-40 hardware from servocity, the 4-40 screw should fit in the stock holes. Enlarging the post holes to .25" isn't a big deal as the stock posts have a tab that fits in to a slot on the post hole and prevent the stock post from turning.
I cracked the front post hole because I didn’t enlarge it, I tried to force the spacer in. The spacer is holding firm though and I figure if it ever does let go I can get a new chassis without holes drilled all over it and use the 4-40 hardware. I'm not sure that was my fault either. When I received the MQ there were washers jammed in the front post hole and the spacer slid in fairly easily without out enlarging it like I had to do with the rear post hole.
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I switched to the 4-40 hardware I bought from Servo city and redid the holes in a new chassis by sanding/grinding the tip off a drill bit so it would enlarge the entire post hole without making the screw hole in the bottom of the chassis any larger. Worked perfectly; no cracked post hole, 4-40 hex screws sit flush with the bottom of the chassis.