Set Terrain Resolution

i have some trouble with the terrain, i have three 5000 * 5000 * 650 Terrain, but the texture paint brush is much to large with Brush-Size 1. compared with a real object its like an airplane. but i need much smaler detail resolution for that, that i can paint little Gravel-Ways etc…

I also tried "Set Resoltion, but when i set the heightmapt Resolution (this is the correct setting for my problem, isnt it?) to 4096 it automaticly changes to 4097 and when i click ok it tells me:

Heightmaps above 4096x4096 in resolution are not supported

what can i do to solve my problem?

you shouldn’t use it anyways by the way

a 4k by 4k texture takes up 64mb of video memory thats before mipmapping (33% increase)

assuming 32 bit texture you get

4096 * 4096 * 4 bytes
or 64mb texture

Thats HUGE.
cards can only do a few hundred (cheap cards, i got a 1gig memory, its also 180 dollars still and its an 6800 so its the last series of cards)

Sure I could run it fine but your leaving alot of people out atm