I'm going to remove this post because I don't think it adds any value.

I think if you explained your algorithm for paging chunks it might help.  I am not familiar.

Are you using the tile you are in and also keeping the 8 adjacent tiles in memory?

I am not a terrain expert (although I hope to be in the future).  I would say that I think it is conventional wisdom to find a balance between tile size and paging efficiency.  Why do you want to go larger than 4096x4096?