Would refrigeration shrink my rechargeable batteries?

maybe, if your freezer has an Absolute Zero Kelvin setting.

How much shorter do they need to be? Can you not sand off a bit of each end?

Be sure though, that the rechargeable circuit is not made for NiCd if you put in NiH batteries. (Explosion may result.)

Newer charging circuits (NiH) are 'supposed to' recognize NiCd, and either refuse, or charge them according the proper rate / duration / charging rate change per amps already pushed in this session / whatever. I'm not sure, but perhaps the slight length difference is a safety feature built into battery specs to prevent this. You really do not want to explode your batteries. Even if you avoid the shrapnel, the contents are caustic and poisonous.

Also, if you do manage to fit them by cooling, don't you think that they will expand again afterwards and probably break the battery holder?

Never thought about sanding the ends of the batteries....does anybody think there could be a downside to doing that?

The radio was made to use Ni-Mh batteries and that's what I have.

I don't know if rechargeables might be different, but regular batteries seem a lot longer than they need be, with that long button. There's nothing in there but more metal, right?

I have a VOM that uses a 9v battery, and it will only take alkaline. Carbon zinc are longer than alkaline and don't fit. Who knew?

Should work fine. Just be sure to leave the radio in the refrigerator all the time. Otherwise the batteries will expand and become lodged in the radio.

Might need a small electric heater. When the radio chills, it will contract about the same as the batteries, and you will lose the advantage. Need to keep the radio warmed.

Probably not much metal, till you get to whatever is in there. Chemical soaked fiber, or some thing.

I missed your issue, are the batteries too long, or too wide?

Reading again. Slightly too long. When I was a kid, I did tear some batteries apart. Some cells, the negative end has a kind of decorative plate, which is held on by the plastic wrap. Don't know if it applies to your cells, but the negative end may have a part that can come off.

The ends would corrode, and you'd lose contact. You could try squeezing each one slightly in a vise. The positive end should compress some...

You might sacrifice one first to see how thick the end plates are. IIUC, you actually have 6 surfaces that you can plane down a bit. Also, a vice might shorten them without breaking the anode or causing an internal short. You might try a combination of both techniques.

(I know not if they do have a central solid cylinder similar to the carbon rod in a carbon-zinc battery.)

Excellent. Be very sure of this. That disclaimer about exploding batteries is not just something the lawyers added to protect them in the one per ten thousand range. If you put in the wrong type (especially a lithium) you are courting disaster.