iron-list loading many hidden items?

[Kelly St. John]

Is it normal for polymer's iron-list element to load a bunch of unused/hidden list items, even though it is actually only passed a much smaller number of array items to its `items` attribute?

I have an iron-list that is currently passed an array 4 items long, but is provided screen real-estate for a much longer list if needed.  Yet, when I inspect the rendered iron-list element in Chrome, within its 'items' div is 4 visible items and 16 hidden items.  I'm thinking this might have something to do with preparing for scrolling/paging of the list?  If so, is there a way to prevent the iron-list from doing all of the work of rendering / 'readying' item templates that are not needed for smaller arrays?

I'm noticing a similar occurrence elsewhere in my app, where an iron-list is provided an array with length of 1.  This is really problematic in that case, as the item template for this list contains a more complex custom element, which is then 'readied' 20 times instead of once.  This really has a huge impact on the app's load time/performance.

Hoping there is a simple solution here, and I don't have to reconsider my use of iron-list in this app.  Perhaps I'm doing something incorrectly.  Thanks!

ps:  Will post SO question on this as well, as soon as my 90 minute wait time between new posts lapses. ;-)