Chuck,
It's too bad you haven't been able to get out. You are going to enjoy hunting with this detector.
I started with 50 CO tones and discrimination also.
I have made several different modes with various degrees of discrimination. Some very tight, just open to the FE/CO numbers of the TID coin numbers I've found on this forum. Then open it up a little more to allow for the cursor jumping around some. I have one for modern coins that's not too tight. I have one for old and new US coins that is very tight. I have one that is almost the same but opens up a little more to allow a little more jewelry. I don't really know yet if it is a good idea to have such a tight pattern as some I have made. The reason I am using 'All Metal' is explained below.
The following is what I have found as a 'newbie.' It's just my opinion, preferences, and as a newbie, I'm sure errors in there somewhere.
The reason I have been lately using 'All metal,' is that when you have targets discriminated out, the threshold will blank for a moment. The detector will go silent. As I understand it, that means the target tones will also be 'blanked' for that moment. That makes a slightly greater possibility of missing a good target close to a bad target. The bad target will make the detector go silent with no threshold hum, and no target tones. I decided to run with all metal so that the detector will not be blanked for that moment, making it a little less likely to miss a good target. I use tones in combined mode.
Be aware that Minelab's software for the CTX makes 'good' targets invariably read around the 12 FE line. You can set that lower large box of the combined mode to lines 13 to 15 FE. If you set it at 13, the detector might momentarily read a good target, especially on the first sweep, at 14, where you will get a low tone for a good target. That could make you miss a good target. If you set the lower box at 14 or 15, that will allow for the detector misreading the target on the first sweep, and make it more likely to get a high tone for a good target. I rely a lot on the display. If I get low tones for ferrous targets, I look at the display to see if I also get a cursor in the 12 line area. If so, I investigate the target a little more closely to see if I can tell what's there. With the lower box line set at 15, it's not too likely to get an actual ferrous target that reads in the 14 or 15 ferrous line.
When using 50 conductive you are generally looking for high tones for a coin. The problem that I have found is that something like 80 percent of the targets you find are targets that read with a mixture of a little 12 FE line good target signal, but have a majority high ferrous/high conductivity signal. They read in the area of 48 to 50 ferrous, and around 38 to 48 conductive. So, most of the targets give a high tone, just like a coin, but are just ferrous junk. But here also, all it takes is to pay attention to what the screen is also telling you. I use the combined, so that when it's ferrous junk, I 'hopefully' get a majority of low ferrous tones from the detector instead of high tones.
Weather you use 50 conductive or combined, relying on the display is a necessity because it is so helpful. Using 50 conductive or combined is very much a matter of preference, and probably sometimes a matter of the conditions. Although right now, in my limited experience, I prefer combined. Writing this, I was thinking of some good points to 50 conductive, and am going to go back and play with it some more.
In the past, detectorists have relied very much on being able to decipher the tones that the detector makes. I wonder now, with the versatility of the CTX display, if the tones may become the initial alert to a good target, and the display the dominate feature to determine what the target is?
