I built several city blocks so far. For a 2 mapsheet city battle, I need 8 'blocks' of 3x6 hexes with 1 hex border of road all around per mapsheet. I have a few smaller irregular building clusters glued up where the rhomboid blocks dont perfectly fit, but ran out of buildings after making 12 city blocks. After starting this city project, it made me really appreciate just how many buildings go into just a simple 1x2 map realistic city. I ordered some more mdf buildings to finish the project, probably not going to arrive till January though.
EDIT: as a follow up, I laid out the tiles on a 2 mapsheet board in megamek. The rhombus pattern made a southwest-northeast running 2 hex wide 'main road' for east/west, at 31 hexes long, presenting interesting sniping down the main thruway. The west north road and east south secondary roads end before crossing the whole map, but allow for some back alley fighting through the north/south roads when trying to avoid the 31x2 hex 'sniper' highway, as the 2 center city blocks must be fought over as they strategically control east/west passage across the city besides the 'sniper' highway. This 2 map sheet layout looks really good for balanced city play, with no easy route for recon/objective grabbing but opportunities for all kinds of back and forth gameplay, and 2 actually important center map city blocks that need to be fought over. With a 3 wide block, you also need 8 jump if you want to cross more than 1 block at a time without using one of the main or secondary throughways, meaning you cant cheese the map with jump jets unless you are packing a LOT of them--so spiders and Ostscouts benefit, but not necessarily assassins or phoenix hawks.