No doubt Fuaga would be a monster at Guard, I just think he'd be a much better RT than Penning. Penning has come along well, but I don't think he's yet to the point where you don't look at ways to upgrade at RT and I have some concerns about giving him a big long term contract. I also think you can probably get some good starting Guards in the 2nd through 4th round of the draft.
I'm particularly concerned about what happens with Penning's progress if we change the scheme and/or Benton and Dennison leave.