FCS/I-AA teams no longer have a 85-player max (I do not believe). I think the max is on active fall roster.
Now a scholarship in DI is split into tuition & books ...and room and board. In I-AA/FCS they can split any way that they want (these are called equivalents); however, most split in these two parts and thus have 126 partials (or 63 full-rides). Now, this is important because you can begin to see the NCAA's purpose in offering I-AA scholarship equivalents is to recruit locally ...thus not need the room and board, as you can offer more than 63 tuition partials. Unfortunately, most good athletes know this and demand full ride, as they travel to play ...look at how many Florida, PA, and CA players we have. Do you think that they will play at YSU for tuition or room and board only? Not likely. It is important to remember that ALL DI schools (FBS or FCS) must maintain a minimum of 76.5 players on athletic scholarship.
In IA/FBS, they have 86 scholarships, but even if a player only receives a single dollar ...it is considered by the NCAA to be a FULL scholarship. So there is absolutely no splitting/equivelants. However IA schools can save athletic scholarships in the same way as their I-AA counter-parts. That is, get aid in other ways. Academic scholarship being the most common. If a player is smart enough to obtain more than a 3.3 ...then they can usually get academic scholarship, then will only need the room & board component of their athletic scholarship. Thus leaving the tuition and book half for another player; or in IA/FBSespecially, they reduce their $$ outlay. Likewise if a team can recruit locally, then they can live at home and save the school the room & board component. Thus it is so very important to recruit locally.
There is also something called scholarship deferment, which is a source of much (cough, cough Urban ...clear throat, clear throat Myer's ...achoo achoo Florida) cheating. We will not get into that as it is too complicated.
However one thing to point out is that a player only has 4-years of eligibility ...no exceptions. From the time they take their first snap (let me repeat 'first snap') in a varsity game the clock starts ticking ...they have 5-years to play 4-years of football. There is absolutely no truth to the fact that a player can play less than 1-game or 1-quarter and can still red-shirt. If they play a SINGLE DOWN, it is like playing the entire season. Amount of time played only impacts a player when he applies for a "medical" red-shirt.