I'm in the process of converting adapting the latter half of RotRL for my group.
(Adapting.convertig because a), the 3.Aotrs houserules we use fall somewhere between 3.x and PF and b) regular party size of eight characters.)
My current projected level for the PCs by the end of Spires is only 15 - I kind want to push them up to at least 17 as intended.
My usual method of dealing wth the XP balance for the larger group is to either double the number of monsters, splash in fewer, stronger classed enemies or add my "Defiant" template [1].
Problem is Xin-shalast is... kinda short of encounters as, written. Given the competance and power of my group at the level they'll be, I'm already liberally splashing class levels and Defiant templates, but even with that, I'm thinking I'm going to be a bit short.
(Example, the four cloud giants at D: giant Sentinels have gone to Fighter 3s, supported by a Cloud giant Oracle which I pulled off the PFSRD (presumably it's a boss monster from one of the other APs or something!), which might provide eight (projected) level 15PCs with slightly more than a speed bump,)
Problem is, I've found with the last the modules of this AP, there are a loot of encounters were (because of space or just encounter structure), it's not so easy to do my preferred "and his best mates, the x-2th level cleric." I can probably make up the short-fall with "random encounters[2]," but that might be a bit... bland.
So, what would be great is if I can crib the brains of the folk here to suggest some possible Stuff I can bung in, to spin it out a bit. Encounters you used, suggestions for other Paizo material set in Xin-Shalast (I transformed the four-Stone giant encounter at the Storval Stairs in Fortress of the Stone Giants into an adaption of the Kill of the Storval Stairs PF scenario, for example), plain old brainstorming, etc etc.
Anything might be helpful, even to ridgely define my areas of doubt and uncertainty!
(This is - believe it or not - the first AP I've run (it took me YEARS to get to the point we were ready to run the first one, and we've only just started Shackled City...!) and the XP issues are... not ever so clearly marked. Also, my XP system i not standard: I typically award half XP for combat (except for RP/story awards (includng haunts) and "boss fights," none for traps that are simple "roll to detect/disarm.") Granted, there are plenty of "boss fights," for which the Defiant template is spammed, but there's only so many times you can take the solo monster ofr fout PCs and go "and double/triple the nuber of hit points...!")
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[1]In short: each application of which increments a monster's hit points, gives it a free save reroll at the expense of effectively negative level and the ability to expend a whole increment of hit points to make bad effects/death go away (ala 3.5's Iron Heart Surge (as RAI!) from the Tome of Battle. Each application shunts the CR by 1 (though I really only use CR a method for calcualting XP; I ignore EL completely). It actually works REALLY well for our play paradigm.
[2](I tend to not use random encounters on the fly (since they make for pretty mundane combats, but pre-script/generate them ahead of time, giving them a tiny bit more flavour.
Yes, of course there is! I'd only half-forgotten that!
I knew I'd read something else beyond the AP about it at some point, but you've saved me the trouble of rooting through all my PDFs to find which one, at any rate! So that's a start.