Etrex 20 - transparent-only mapset not listed on device

[lsglass]

I am loading the Etrex 20 with maps for a Continental Divide Trail hike.

I have loaded separate mapset files for each state - NM, CO, WY, and MT/ID. Separate in the sense that they are in multiple .IMG files - New Mexico.img, Colorado.img, etc.

I going off the CDT corridor for a while around Yellowstone, so I also included some NW trails and/or mytrails maps with the WY and MT/ID files. 

All of this is working fine, as far as I can tell.  I can see the trails overlaid on the topo maps.

But then I got to thinking I would like to just have the trails-only in a mapset by itself.  Without altering any of my prior work, I uploaded the NW trails as a standalone .img file.  It did not show up on the device in the list of maps.  I tried the default GMAPSUPP name, a non-default name, no dice.  And the trails do not show if I go look Wyoming and Montana on the map screen. (All of my other mapsets disabled.)

I also tried the same process with the mytrails map.  Same result.  Montana trails V3, ditto.

Then I tried including a tiny slice from one of the nontransparent topo maps in with the transparent trail maps.  This caused the mapset to be listed, along with the others, on the device.  But while these maps were enabled, none of the transparent trail stuff displays when I go to look at the map page, I tried all the zoom levels.  The tiny bit from the topo map (which was in CO, while the trails were in WY/MT) does display, however.

As I said, I tried the three different transparent trail maps, and none will display when loaded alone.  But I tried the transparent Montana Wildernesses as the only map in an upload,  and that does work?!

I've tried many different approaches and can't get the trails-only maps to display - save for one out of many tries, I think.  And then I screwed around with it and it didn't work again.

All of this is transpiring on the device, no use of an SD card.

Sorry, very long-winded.   Shouldn't a mapset of only the transparent trails be accessible on the 20?  Is this a bug, or am I not understanding something?

Thanks for your assistance.

[Boyd]

There was a bug in some of these transparent maps that caused similar problems in the past. I thought it was corrected by the author however. Are you using the newest versions?

[lsglass]

They were all downloaded in December, so they should be pretty new.

Sounds like I should be contacting the authors, then?

[lsglass]

I will contact the authors.

Thanks for your help!