as James said , it will only work in you let Pscan handle the UV ...
Other idea
_ Duplicate your chunk 4 times..
_ In 3dmax, split your model in 4, for each part, refit your UV to occupy the max ..
_ In each chunk, load one part of the split model, rename the chunks if you want..
_ Texture each part with 13.000 pix (as it's your max)
(advice, for each chunk, you can disable the images not needed)
now you end up with 4 parts, and each has a 13.000 pix map, so right there you have doubled your res.
hope that helps.
f/
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