L3-LL Ultramaximizer or Multi-maximizer Sidechain?

I don't think the L3-LL has a side chain function for external side chaining. 
That's because it is primarily designed for mastering. 
Is that correct?

Yes there is no side chain on this one but I must say as a loudness maximiser it is one excellent plugin.  I am using it in a mastering session at the moment and I have got it adding like 6 dB or more of rms gain and none of the bands are even being hit by the signal at present.  This is quite extraordinary in fact.  It has the potential to add a lot of rms gain before even the individual bands are being hit.  I certainly prefer it in multi band mode that is for sure.  Also the output gains of each band can used as a final EQ process over a mix as well. Which is very handy for a final fine tune.
 
In terms of adding loudness before it imposes any sound, it is ahead compared to say Xenon. That limiter can also add loudness but you can see it working while you are doing it though. (And hear it sometimes if you push it hard) With the L3 it hardly ever works hard and seems to add a lot of rms gain rather elegantly and effortlessly at the same time.  
 
Being last often it is also important that you set things up very well prior to it too.

i actually like the L2 better for mastering.
don't know why exactly, the sound just seems...... cleaner.
 
maybe i'll experiment with the L3 more when i get my new daw built.