<<I still recommend adhering to the published CG limits, but when push comes to shove there is more wiggle room at the aft end of the range with the larger tail.  Even with that cushion, some have pushed too far.>>

 

Chris is correct.  The forward CG is generally limited by the ability to flare on landing, i.e., having sufficient "control power" to lift the nose at low speed.  That's a pretty objective measure.  The aft CG is generally limited by handling qualities.  The handling qualities get worse as the CG moves aft.  In this context, "worse" means things like stick-force-per-G and short period damping.  Whatever the specific aircraft parameters are to an aerospace engineer, to a pilot it just gets "squirrely" as the CG approaches the aft limit.

 

Where the aft limit is, well, that's purely subjective.  What's acceptable to you may not be acceptable to me.  What's acceptable in smooth air may not be acceptable on an ILS to minimums.  It can also be mission-dependent.  What's acceptable for an acrobatic airplane may not be acceptable for a trainer airplane.

 

In general, the handling qualities are improved as CG moves forward or as tail size increases (although the precise mechanisms are different and it's rather an academic discussion anyway).  The main reason we're having this small tail vs big tail discussion is because we all have different thresholds of "good enough". 

 

- Rob Wolf

Large tail and proud of it...

Also not flying yet and kinda embarrassed by it...