Airport Extreme Base Station A1354 extended network

[BC2009]

Ok, so my previous Airport setup was 1 x AEBS (model A1143 -- dual band, but NOT simultaneous) with the network extended by 2 x APE (model A1264 -- again dual band, but not simultaneous).

My new setup is 1 x AEBS (model A1354 -- simultaneous dual band) extended by 1 x AEBS (model A1354 - simultaneous dual band) and 1 x APE (model A1264).

So the "Apple Expert" who called me to give me support told me a couple of things and I wanted to confirm.

He said if the secondary AEBS (A1354) will extend BOTH the 5Ghz and 2.4Ghz band versions of my network (I'm NOT using the guest network feature). Thus far I can confirm that the 2.4 is indeed stronger in my office than it ever was and when I positioned the secondary AEBS next to the mac mini in my kid's playroom it bound to the secondary AEBS on 5Ghz channel when right next to it.

So he seems to be correct about extending an AEBS with an AEBS when both are A1354 models.

However, also on my network is the APE (model A1264) -- no Airport Express has simultaneous dual band, so my big question is -- which band is getting extended? Is the APE running at 5Ghz or 2.4Ghz ? I cannot find any way to manually choose a band for the device in Airport Utility (and Apple Expert confirmed the same -- he said it was automatic).

Can anybody provide any insight here as to what is going on with the APE?

FYI, I set my radio mode on the primary AEBS to be: 802.11n (only) on 5.0Ghz and 802.11 b/g/n on 2.4Ghz -- also using "WPA/WPA2" mode to support an older device that only has WPA.

Thanks for any information.