There isn't a definite way to verify the size of a recording, CTDay. The HopperGo does have space for up to 100 hours of media content. We can try to base it off of the typical bandwidth of an IPVOD. https://www.mydish.com/support/general-speed-size
For lower-action content, it's about 0.6 GB for SD and 1.1 GB for HD, per hour.
For high-action content, it's about 1.7 GB for SD and 2.2 GB for HD, per hour.