Can you use a service like Dropbox to provide additional information. That way you can cut the background explanation to a minimum and if they want to look up your methodology etc they can just download it from your public files in Dropbox (or similar). Put the URL of the files up on screen while you give the intro. 20 minutes for a presentation is nuts - the conference I go to gives speakers twice that.
The problem with using add-ons for a talk is that yes, you can offer them for anyone interested... but the information is not available during the talk. And methodology, in this case, is something I want to cover (or at least mention) during the talk, due to different special methodical problems with textile crafts connected to the experimental approach.
And 20 min is quite normal for archaeological conference talks - it just means you have to learn how to give intros in a very short and concise manner. Mostly, I don't mind that restriction too much, but the spinning experiment is a really huge topic with lots of necessary background explanations...