I have all my buildings portaled and about 20% of the outside and they all work
I use the NTSF compile method
I have a Max_Map_visiblity exceeded when doing vis and flare so I kept working on portals trying to bring that down but I have noticed that the visdatasize is going up with each portal I make.
I have made all parts of my buildings detail except the outside walls and all outside fences, etc detail trying to cut this down some. I don't have any real errors compliing except for some textures not merged for pointing the wrong way.
any ideas?

IF your terrrain has any brushes, make sure they are detail also. terrain and patch meshes are detail by default even though they don't show that way.

Portals do move the visdata size up. Is your map big and/or is there a lot of models?

I have or had 818 models (various trees, bushes, furniture and a few vehicles) and 4900 brushes

the map is about medium sized for about 30 to 40 players.

I have deleted models so its down to 650 models with no noticeable difference in visdatasize.
not sure if deleting anymore models would help and then the map would be completely different .

Visual data size can be extremely large with just 40-50 brushes, it depends on how BIG these brushes are.

As a comparrison, my remake of the Brecourt Manor map, as seen in the Custom Map Forum is currently 90000 visdatasize.

I used an aerial photo of Brecourt to lay out some trees and simple single brush hedges and some 10 terrain meshes to form the ground.

I deleted the single large brush textured with the aerial photo and put a skybox around it (24000 x 24000 x 3000 high)

At compiling these few brushes had a visdatasize of 325000 !!! that is 3 times the size of a more complex map.

Its all to do with the size of single brushes. The skybox is very large in plan and some of the hedge brushes are 12000+ units long.

Its nota problem if you only compile with fast Vis, but could take several days to compile with full vis.

Hope that helps