I'm not a fan of IFA on a medium TD. The Medium already has a high rate of fire and to add in-penetrable front armor is ridiculous. Su 76, 85 and even the 100 was quite easily penetrated by the PZ IV. Even a Jgdpz IV was vunerable to the sherman 75mm.
Implementation of this shield (IFA) should be limited to Heavy TDs like the JpdTgr, Elephant and Jpdpthr. Maybe the ISUs if you wanted to promote the fixed gun tank, but even that is an issue because the PZ IV could knock em out frontally at close ranges.