My local supplier brought in a Nardo and M15 for me to test. At my local track (very technical layout on medium grip grey ozite), i tried both bodies on my 17.5 touring stock car. The M15 was very easy to drive, and very consistent. I put in a good run, although my fast lap was 0.2s off of the pace with my previous body. The consistency made up for the lack of speed. I then tried the Nardo. It definitely had more steering, but it wasn't hyperactive or overly sensitive to steering inputs. The rear was a tad free, but very easy to control. The car was very close to grip rolling with this body compared to the m15. I figured this would be a good mod body.
I then tried it on my mod car and was instantly impressed by how well it worked. Running modified touring on our small tight layout is difficult, but the nardo allowed me to run 5 minutes without even a board tick.
This past weekend, i took the bodies to the 4th leg of the WCICS series in Edmonton. The event was run on black crc ft2 carpet. I brought 9 different bodies with me to try. I ended up coming back to the Nardo for all of my runs in mod. It had the perfect amount of steering and rotation while still being forgiving. Blitz gsf wanted to get loose on throttle, ltc2 would lose rear traction a bit more suddenly in tighter corners (not to mention the ltc2.0 was WAY more prone to cracking). Blitz wrx gave me grip roll issues.
I was not able to run the M15 at this event. Some bumps on the track meant that the bodies had to be mounted a bit higher than usual, and i wasn't able to mount the m15 high enough due to bit having high enough body posts. The m15 requires VERY long front body posts due to the hood being very long and high at the front.
Biggest downside to the Bittydesign bodies is their weighg. They are very heavy compared to other manufacturer's lightweight bodies. It looks like this has been rectified with the new material supplier, but it may take some time before the old heavy bodies get through the system.