- Stocking a hospital was near impossible. I'm still not sure how to make sure you have everything you need. Previously, if you put a bunch of coffers in the hospital, the dwarves would go nuts and fill it all with cloth, ignoring anything like Gypsum Powder.
- Gypsum Powder from trades wouldn't show up in the hospital
- No stockpile option for Gypsum.
Fully stocking a hospital is now possible, but can take some micromanagement.
The amount of each item your hospital is set to need is extremely important, and is probably the most important thing to control. You control this through using i H over an already designated hospital, in case you didn't know.
The sequence of checks appears to happen like this:
Does the hospital need more of something and is there any space for more of something then create a job to bring all available something to a hospital coffer that had room for it when this process started.
The checks do not look for how much something is available and how much space there is, nor does it compare how much is available to the current need.
If you need 1 more thread to meet the hospital's thread need and have space for one thread in the coffer and you make 1 thread and wait, one dwarf will rush that thread to the hospital. The need is filled/the space is used, so there's no hospital demand - create as much more thread as you like and it'll be stockpiled normally.
If you have that same need and space availability but have several looms and make multiple threads at about the same time, every thread will trigger a 'take me to the hospital and put me in that open space job' until one of the threads actually gets there. Then new carry and place jobs stop being issued - but the other dwarves carrying thread to that coffer do not get a cancelation notice. Even though the coffer is now 'full', there's no second check to make sure it still has space, so the dwarves place the thread in the coffer anyway, leading to some really full coffers.
If you have that same need and space availability but a caravan arrives with thread aboard, apparently your dwarves will still raid that caravan for thread. I think I read that they won't even wait for the caravan to reach the depot, they run and 'snatch' thread as the caravan approaches, until they either have all the thread or the hospital demand/capacity is filled. Since caravan's rarely have much thread, this often is all the thread the caravan had.
How I handle this - I modify my hospital's needs so the only thing it needs is Gypsum Powder, which I bring about 20 of on embark. I usually get my hospitals up early to get that powder stashed away. I usually 'get the materials', then increase the hospital's capacity through them, then after the rush is over, use i H to check my capacity levels (whoa, 120000 of 4000 thread, yeah) and then t to check each coffer and then mark what I don't want in there for dumping, then reclaim the dumped items. This frees space for any other items I need and makes sure that my dwarves are using the cheap plentiful threads instead of the expensive rare types for the suturing to come. Just don't dump powders, they spill and are wasted.
Note, you can store gypsum powder in a stockpile set to furniture. It's considered a container and gypsum powder as well as the respective quality modifiers, as long as the stockpile accepts those you can restrict fairly closely (dwarves will still place empty containers of all sorts there as well - and sometimes place seeds in any empty bags, but at least you know where all your plaster is).