Charge rate

Check all your connections in particular both of the yellow wires from the AC generator connected to G on the regulator. If the charge system gets overloaded these two connections get hot and loosen up. Pull them out of the black regulator connector and use a pair of pliers on them to make sure it is a tight fit. Then reasemble with dialectric grease.

https://www.permatex.com/products/lubricants/specialty-lubricants/permatex-dielectric-tune-up-grease-4/

This seems to be normal in many aircraft and can depend on your instruments. For example the Flight Design CT always reads .5v low on theinstruments. So when the system is charging at 13.9 it is reading at the instrument 13.4. This seems to be pretty common.

A lot depends on where you are measuing the voltage.
There is a small but not insignificant voltage drop across every wire.
The regulator could be at 14.2, The battery at 14.0, the Master buss at 13.8, and the voltmeter at 13.6.
Turn ON and OFF a heavy load (All the lights) and see if the voltage changes.
If you see a 1/2 volt drop, that is the wiring.  The Regulator and Battery didn't move more than, 0.05v.
If you see 2v change, I would look for some loose connections.

With the engine OFF and the panel loads ON ...
Measure the voltage at the actual Battery Posts (Not the Clamps) with a reliable hand meter and compare it to the panel voltmeter.
12.6 vs 11.9 would not be suprising.

As long as the engine starts without requiring an external charge between flights, The battery is getting charged sufficiently.

I think the original poster's concern is that his charging voltage is varying, not constant.

How (not where) is the voltage being measured? Can you set up an alternate way of measuring the voltage and see if that shows the same variance?

I appear to have stumbled onto a solution. The wiring coming out of the bottom of the regulator was very close to the radiator hose and may have been affected by the heat generated inflight. I moved the wiring away from the radiator hose and am now registering a continuous 14Volts.

Thanks everyone for your help.