On low-end (512MB) Android, we currently have a hard memory limit of ~100MB and a soft memory limit of ~64MB. 

Having a high hard memory limit is reasonable (we want to display page content, and if we need the memory to do so, that seems fine). However, the soft memory limit seems way too high.

On a typical 512MB device with a 720p screen, a full-screen layer is 768Kb. Our soft memory limit allows us to keep ~80 full screens of tiles in memory before forcing eviction.

Consider dropping the soft limit to 5 or 10MB.