A bit more careful reading of instructions and practice with Moagu produced graphically good results; non-grainy image, simple legible colors, legible lettering and though slow to refresh, is likely speedy enough for a small slow sailboat. 
Here are the settings:
•color setting: "checked"
•scale: 800
•tile size: "large"
•contrast: "left unchecked"
•combine: "yes"
Results
*File size: 114 tiles, 94 Mb
*Display colors: non-grainy; land, tan; shallow water, light blue; deep water, white; lines, black; buoys etc., river mile markers, red. Numbers and letters are legible black.
*Refresh time: much better than the first attempt's 137Mb file. Ok for sailing.
==============
Misc.:
*Tile setting "small" gave nice colors, 538 tiles, 201 Mb, and super slow refresh rate
*Checking "contrast" (with large tile size); colors were black, white and red; yielded 252 tiles at 58 Mb, good refresh rate but difficult to discern land from water because both were white.
Overall? Neat product. Maybe not as fast as Garmins' nav charts (have not tried 'em and which anyway do not seem compatible with the etrex vista hcx), but graphically good, the price sure is right and it should work ok for the nearby river. Plan on trying chunks of Puget Sound next.
Cheers to the developers! For those folks just getting their feet wet with this product, I worked my self into a blind alley more than once. Keep trying. Keep reading the instructions. What helped greatly was to set up a unique map file name for each run,#####_#abcd, based on chart's number with letters indicating key settings. For each run, record the file name, settings (map number, which settings were used, etc.), and outcomes (tile number, file size, colors, refresh rate, etc).
Best, Forester
p.s. 20120218, Discovered that the NOAA chart disappeared from the Etrex when batteries are low, however, it reappeared after installing fresh batteries.

Here are the settings:
•color setting: "checked"
•scale: 800
•tile size: "large"
•contrast: "left unchecked"
•combine: "yes"
Results
*File size: 114 tiles, 94 Mb
*Display colors: non-grainy; land, tan; shallow water, light blue; deep water, white; lines, black; buoys etc., river mile markers, red. Numbers and letters are legible black.
*Refresh time: much better than the first attempt's 137Mb file. Ok for sailing.
==============
Misc.:
*Tile setting "small" gave nice colors, 538 tiles, 201 Mb, and super slow refresh rate
*Checking "contrast" (with large tile size); colors were black, white and red; yielded 252 tiles at 58 Mb, good refresh rate but difficult to discern land from water because both were white.
Overall? Neat product. Maybe not as fast as Garmins' nav charts (have not tried 'em and which anyway do not seem compatible with the etrex vista hcx), but graphically good, the price sure is right and it should work ok for the nearby river. Plan on trying chunks of Puget Sound next.
Cheers to the developers! For those folks just getting their feet wet with this product, I worked my self into a blind alley more than once. Keep trying. Keep reading the instructions. What helped greatly was to set up a unique map file name for each run,#####_#abcd, based on chart's number with letters indicating key settings. For each run, record the file name, settings (map number, which settings were used, etc.), and outcomes (tile number, file size, colors, refresh rate, etc).
Best, Forester
p.s. 20120218, Discovered that the NOAA chart disappeared from the Etrex when batteries are low, however, it reappeared after installing fresh batteries.