Of course I'm trying to get the max final volume, but I see the red light (between the "Post" and the "Off/On" buttons) on the Master flashing at me and assume i'm over driving it, even tho it is not peaking on the meter. 
Is this a bad thing and, if so, what do I look for? (It does sound a bit raspy)

I always trim the gain stage at the top of the Pro-Channel when I see this type of overdrive happening.

What type of instrument is it, and is the red light staying on a lot , or just occasionally ?

I find it happens a lot with bassy synth plugins, especially ones that are limited or compressed a lot, so I usually have to trim their input stage.

(PS . . . how old are your Yamaki acoustics ?  I currently record using one made around 1970)

That light is not the master channel clipping, it's the master ProChannel overloading. 

First thing to do is get your console open and check to see if any of your track PC lights are turning red as well. If they are, then that overload is going to be reflected in the master PC. Reduce the gain in the track PC that's overloading. 
If you still see overloading in the master PC then either move all of your track faders down until it stops, or like noynekker says, trim the gain using the gain knob at the top of the master PC. 

My rule of thumb is to look at the console view. 

Keep the tracks out of the red. 
Keep the master out of the red. 

If they "bump" the red, no need to sweat it.... you don't want them constantly bumping the red. 

Adjust the mix as needed to keep everything running in the black. You can ALWAYS turn the volume up in the mastering/polishing stage, but, it is critical to get a clean mix first and foremost. 

If by "out of the red" you mean the meters, then I have no problem there. It's the PC light I was referring to.
I have busses for vox, guitars and drums and they are all just starting to glow a light colour just like the various trax.

Its a balancing act when determining the volume levels for the plugin effects on buses and the send levels of buses for each track. 

Each song will need different levels set just right so there is no clipping or over-saturating the master bus or any other bus or track. The gain stage in a song is very important. Treat it with great respect.

Cj

An important thing to remember is that none of the track's ProChannels can be overloaded by faders as long as their ProChannels are set to "pre" rather than "post" - rather, they overload when the inputs to the ProChannels are too hot. The master bus, however, can have it's ProChannel overloaded by the track faders, since they are summed into the master ProChannel. If that makes sense :)

Ok, that does make sense now. es all the "Post" buttons are not lit up.
PS thanks for the tip about the gain on the Master PC

And yes I am just now "getting" the idea of "Less is More" with the faders. IOW pulling the rest down instead of just boosting the one you want clearer. It's counter intuitive to an old band guy who's traditional way of being heard was to crank it to 11.

If I am redlining I usually mas select all the busses including the master bus and CTRL drag the faders down to give me more room then carry on writing.

This leaves you plenty of room when going into the final mix procedure.