it is possible to insert a tuttle in a deeptuttle box so you don't need to narrow your search to deep tuttle. You just have to add longer screws (90 mm i believe) and it'll fit.
As for fins: the freeride flow seems like a good fin. Personally i've always liked the R13's made by Drake. Real fast fins and good early planners with a pure slalom design and feel.
If you're willing to look into other, cheaper or more available brands and in the freeride range i've always like the Select ride series. They come in every type of box from power to deep tuttle and the price is very good in comparison to the performance. These are very controlable fins with a good top end speed.
I've also heard a lot of good things from maui fin company Liquid Pro and Liquid Move but they're a bit pricier. I own MFC freestyle fins and have no remarcs whatsoever but freestyle and freeride differ quite a bit.
In short, many brands supply good freeride fins but you should try to get feedback before you buy one to see how it works. You can also consider a slalom fin, which you can much more easily find in deeptuttle on the second hand market for a good price.
Haiko, AKA crazychemical