Deployable Science / Cargo Compatability?

[coredumpster]

Is there any rhyme or reason on what deployable science parts can fit in which containers?

I have unlocked the Grand Slam Seismometer, but it absolutely will not allow me to place it in the SEQ-3 ( 3 slot ) container in the VAB.  It does seem like it's allowed in the SEQ-9 ( 9 slot ) container?

No error message, nothing on the right click expanded description.

It weighs less than the Go-ob ED and the Experiment Control station, so it seems like it's rather haphazard in terms of what parts fit in which containers?

A cargo slot should be a cargo slot, but it seems they are not.

[Tonka Crash]

It worked for me. A cargo slot is a cargo slot. I hauled the Seismometer to the Mun in the 3 slot container.

[coredumpster]

I cannot get it to work, even if I pin the window open on the cargo container. 

I can only put the Control Station, OX-STAT, Go-ob in the 3 slot.  Ion, Seismic, and Antenna will only let me place them in the 9 slot.

[StrandedonEarth]

I had a glitch trying to load the Ion detector thingamabob into the cargo container the other day. It just wouldn't go, but other experiments would. But I was soon done for the day, and shut down for the night.

The next day, it loaded into the cargo container fine. So I would say restart KSP, perhaps rebooting your PC for good measure.