It'll be an interesting one and I agree with
@Left_peg comments that Fry playing left side is the only time he's looked really uncomfortable. Although admittedly that was when he was younger and he may now have more experience and tools to make it work.
I also think Fry in general has always been criminally underrated by a large section of Boro fans. Many seem to have decided he is 'weak' and is frequently 'out muscled' despite there not being huge evidence to support this. I've read a few times on here posters describing him as being 'regularly bullied' but have yet to see this consistently with my own eyes. It seems an easy thing to latch onto because visually he isn't as wide as he is tall. The Chelsea cup game from last year sticks in my mind as one such instance where some repeated this 'bullied' claim and I just didn't see it. It seems to be entirely based on one incident in the game where Drogba got the ball into feet with Fry in behind him and Fry rightly stood him up and didn't dive in. This became Fry being 'held off easily', 'thrown like a rag doll' or 'easily turned' which are some comments I seem to remember reading on here in the aftermath of that game (which is rewriting history for me).
I just think as he's more a classy ball carrying centre back some fans have decided he isn't for them because he isn't sliding on his backside coming through the back of the opposition centre forward or hoofing midfielders into the stand. Boro fans (with the odd exception) have frequently favoured the more agricultural type of player.
A number of managers have praised Fry as a huge asset and he is frequently linked with Premier League interest which let's be honest doesn't happen if you're poor (not sure I've ever heard of Lenihan being linked to as many Premier League moves).
I agree with the comments above that Fry is arguably better if playing alongside an 'organiser'. I haven't seen enough of Lenihan to know if he'll be a regular through the middle and if Fry will be displaced (I take the point above about Lenihan being Wilder's signing). However it's a long season and I think at various points we'll have most of the centre backs playing multiple positions by the end of it. There are a lot of games and we'll need them all.