I wouldn't put him in lock as he isn't fit enough to cope with the tackling. When he has to do lots of tackles in the last year and a half he has struggled. Now put that together with Preston's defensive weaknesses and you are starting to get a big problem.
And let me make it clear, There is no problem with his defence, it is just he can't do a lot of it. But I guess you could argue everyone else in the pack is hard workers which could make up for that but it will bite sooner or later.