TLDR: A $20 ROCKBROS front fender (link below) from amazon installed in addition to stock fender as shown in photos significantly improves tire coverage and is compared to the heavy duty Rad Rover 6+ front fender. Adding some rubber/like weather stripping (example product link below) to inner portion of ROCKBROS fender where it contacts stock fender eliminates noise.
So I was fortunate enough to get the Radster Trail on flash sale for $800 through Best Buy. I like others didn't care for skimpy front fender. I initially bought an alternative front fender (SKS Mudrocker) for $44 as recommended on a Rad Owners Forum post, but this only gave me 2 additional inches of coverage in the back and I returned it.
I then found this $20 fender from ROCKBROS to install in addition to the stock fender (see photos). Here is the link:
https://amzn.to/3MxGJqU
I found this to be the best configuration, and it gives nearly 10 inches of additional coverage in the back as opposed to 2 inches. It initially made noise over bumps which I easily fixed by placing some rubberized weather stripping at the contact point on the inside of the add-on fender (see photo). Here is an example product:
https://amzn.to/4crPmhm
I also own a Rad Rover 6+, and you can see the front fender coverage compared. Though not quite as extensive as the RR6+ coverage, it's suiting my needs great over the past few weeks. I rarely need to adjust it. Please see all photos and captions.
I have no relationship with ROCKBROS or Rad Power but I did want to share this awesome bike hack with you all. Happy riding!