I would like to try out an idea, especially since we have some black-belt codicologists here. 

I noticed that in the mediaeval East Indian ms. corpus, we have a larger amount of pre-lined mss. among those dated to Pāla regnal years than the ones dated in the Nepalese style. 

Perhaps I should explain: by pre-lined I mean primarily two double lines separating the margins and the string space(/s) on each side. Secondarily, the guideline for the sūtra to help maintain lines parallel to the edges. Something like this: 

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My survey is not at all exhaustive, and, as I said before, this practice is not unheard of in Nepal. However, it starts in the Pāla realm a little before 1000 CE and continues steadily up to the very end, whereas in Nepal it seems to begin only in the early 12th c. My hypothesis for the time being is that the Nepalese were emulating this habit. Also note that the script in these cases is usually what is referred to as 'rañjanā' or simplified versions thereof. Ok, this last point sounds muddled, but I think that the palaeography for this corpus is pretty weak.

Any comments would be greatly appreciated, especially if you can point me to some secondary literature on the subject. 

Best wishes, 

Peter Szant2