I'm not sure if your (Skinsraj) freeplay was loyalty bonus Bonus Play, but it is my understanding that loyalty bonus Bonus Plays must be used for 1 wager (either straight or parlay). I've had Bonus Play wagers cancelled (after losing them) when I broke it up into multiple wageres. To do the 8 3-teamer thing, you would need 8 Bonus Plays. However, this could also result in the plays being cancelled.
A couple of years ago, you use to have to call in loyalty Bonus Plays. When I would have 2 loyalty Bonus Plays available, instead of playing a straight wager that I liked, I'd put that team in 2 parlays, using both sides of another game that couldn't land on a push.
Bonus Play #1 $200 parlay
team I liked +8-1/2
team X -3-1/2 (X is playing Y)
Bonus Play #2 $200 parlay
team I liked +8-1/2
team Y +3-1/2 (X is playing Y)
I successfully did this and my game (at +8-1/2) won and $520 was added to my account (as opposed to $363 if I used the 2 Bonus Plays on a straight wager).
Some time later (a few months), I called in and attempted to use 2 loyalty Bonus Plays similarly. As I read the 2nd one, I was stopped cold and told that I can't do that. The 2 instances were with 2 different reps (one was Herman and one was Shayla). Ever since then, I generally use one loyalty play at a time and just play regular (uncorrelatd) parlays. Although as I mentioned above, my plays were cancelled when I broke the loyalty Bonus Play up into multiple wagers (over the internet).