Hey there @Crider!
The answer to your questions lies with the rim size. The DRT 1.2 has ST i25. rims. The “i” here stands for inner rim width and the number, in this case “25” is the width in mm.
Check out this WTB rim chart which will help you make your decision. You will see which tire widths are optimal vs which ones are compatible. In your case the chart indicates that while a 2.8” tire is compatible, it is not optimal.
Hope this helps!