Inter-clan (ONLINE) tournament for Heroes 3.

M with a basement for four players is, in my opinion, very small. Castles will be located three days' travel distance from each other. XL is a bit too much, but L+U seems just right.

By the way, here's a small statistic that shows that an XL-sized map is smaller than an L map with a basement, equivalent to two S-sized maps or one S map with a basement...
Let's take the smallest map, S, as our unit of measurement.
S = 1
S+basement = 2
M = 4
M+basement = 8
L = 9
L+basement = 18
XL = 16
XL+basement = 32
So, if XL is considered too large, then L with a basement is even larger!!!
Here's a comparative example:
1. The maps we played in the "Seasons" tournament were almost all M without basements, and those that did have basements didn't really have much of a basement. I wouldn't say there was a lot of room to maneuver, but it wasn't too cramped either... but the maps were mainly intended for 2 players.
2. According to statistics, duels lasted from 3 weeks to 2 and a half months, which is quite normal.
We will have 4 people, so it makes sense to increase the map size by 2 times, and the trend should at least remain the same, or it may even change towards a longer duration.
3. If, when increasing the number of players by 2 times, the map size is increased by 4-4.5 times, then the game duration will also increase by "n" times, where it is more logical that "n" = 2... Well, and who would want to play for 1.5-4 months when 1 month of the game takes about 4 hours of real time!