Hi @Toby, we do not have built in bootstrap support yet. If you need to make your site containers 1170px wide, see this topic to customize a media query in the Header of your site using custom css:
If you have some extra time, please share your thoughts on this here: Support for Bootstrap 3 Framework - Product feedback - Forum | Webflow
I hope this helps. If not, please let me know – I’m happy to assist further! 
Cheers,
Dave