I tried a solo game of Nomad but 64 zombies on horde night and got messed up hard. It was the first horde night and I didn't have any ramps, tunnels, or anything. What I did have was a concrete base, 2 rows of spikes, a row of barbed wire, and double stacked wall of wooden bars in between those rows to slow them down.
I thought this would have been good enough, especially since in previous alphas, 64 zombies just didn't happen the first few blood moons.
I was so wrong. I probably would have made it if I had an AK or if I would have made up some molotovs or something. All I really had to work with were hunting rifles and shotgun. For some reason I didn't even find a single pistol in 7 days of looting, which was a first. Still, I was not concerned being the first horde night with some pretty good defense.
I had to have killed around 70, but they broke through and made it up to second floor. I ran around in tight circles shooting my shotgun, placing my junk turret, healing. I repeated this cycle over and over, coming near to death several times. Just when I ran out of everything, I got stunned and knew I was done, so I turned around to see what remained. There had to be nearly 20 zombies still in play despite all my efforts.
So, yeah... 64 zombies works. I won't be playing that by myself anymore, lol.