Pagespeed insights Low score with UpFront

Hey WPMU,

I've built a site for a company I'm working with in Upfront, but no matter what I've tried, I can't get the google page speed for mobile to exceed the sixties.

I have smush-it installed, images for the home page are around 700kb.
I have hummingbird installed, and optimized the best I can, but am still running into "render blocking javascript" that lowers the score.

I have also tried the experimental features for upfront that change things around to make it render faster. When I try these it breaks the wpmu background image slider and causes the CSS to not render quickly enough (you see non-styled for a second on the page)

Is there any way to optimize for this? This low score will likely have a significant effect on the SEO rankings for the site.