So. I have a problem. - Cutting a map into chunks

Hi everyone:

So. Storytime first: I’m working on an indiegame, with a map thats 2km² big.

Now I’ve sculpted (generated XD) the map and everything (19.000.000 polys) and baked a high map.
(thanks 970)


That High map, I put on a lower-resolution map, so I have a good base going on.
(and I don’t have to sculpt on freakin’ 19.000.000 polys)


So. Next step is to sculpt that lowres map like I want to. I can make overhangs and everything, because in the engine, we won’t use a highmap, but I’ll cut the map I’ll sculpt into 40x40 pieces, make LODs of every piece and use them as chunks, so they are going to be loaded in when the player turns.
I’ll use dynamic topology for that.

Here’s my problem: Let’s imagine my map is finished and I’ve sculpted everything.
How can I cut that giant map into 40 x 40 polygons??
The topology will be dynamic-shitty XD So no way for me to get anything out of that.

I thought about cutting the map FIRST into 40x40 pieces, and THEN sculpting on it, but thats what happens when I try:


So the only solution that would leave me, is to first sculpt the map and THEN cut it into pieces.
How? XD
I hope you can help me…

Have you made any progress with this? I know there’s an answer, but I haven’t quite been able to wrap my head around it.