Multi-zoned grid limit

Hello,
I’m working on Urban Operation, (a street fighting tactical wargame) and I have a question about the multi-zoned grid. In Urban operation the map has a hexagonal grid for outsides (street, gardens, sewer…), but when you enter in a house, it become rectangular zones, one rectangular zone by room. I have thought to use multi-zoned grid, which work on my tests, but on page 33 of the VASSAL (3.1) designer’s guide, it’s written:

Use of a multi-Zoned Grid is not recommended for a map with many Zones.

There are more than 150 zones to create, by map, and there are 4 maps. So, my question is: may I try to create this number of zone, or do I have to stay with a one hexagonal grid, like in the street, it works, but the unit is not exactly in the center of the room.

best regards