ControlLogix with Flex I/O and "spare" slots

Is it possible to leave a "spare" terminal base for future use with 1794 Flex I/O? In other words

1794-AENTRXT
slot 0 - 1794-OE4XT
slot 1 - spare base for future use
slot 2 - 1794-IB16XT

I'm used to 1756 chassis with fixed slots.

this is my second message as my first was wrong....

you use the bus connectors on the base, so the communications should be there.
Will you get a rack fault indication if there no module in slot 1?

Why can you not put a digital I/O module in there, leave it powered up, but no I/O involved? If you need to change it at a later date, then you can....

I think you can use this:
"1794-N2 FLEX I/O Dummy Filler Module
This module is used to fill in an otherwise empty slot: a terminal base with no
I/O module. It contains no electronics."

See pg 126 here:
http://literature.rockwellautomation.com/idc/groups/literature/documents/sg/1794-sg002_-en-p.pdf

In the case as described, you can leave an empty slot in between modules and the diagnostics will simply show a module fault for the empty slot. The rest of the devices will function normally.

You can't put "reserved" slots to the right of occupied ones and configure your Studio 5000 I/O tree for the future devices, because the FLEX Adapter determines its "rack size" by examining the FlexBus at startup. The rightmost detected module determines the actual rack size, and it wouldn't match the configured size in the program.

I would go with a dummy or potentially the cheapest IO module you could get to be sure the pins on the backplane are protected.