Tretter didn't fail to keep the C position, he lost it due to injury. Linsley played great, how do you justify the switch?
As for Barclay's contract, that's presumptive, but conceivable I suppose. That said, DB came out of nowhere at LT much like Linsley. . You don't overpay BB because you anticipate having to spend the same money at the position in 12 months.
Yet again, I want to reiterate I'd feel more at ease with BB at RT, but i also acknowledge that in a capped league, you have to be responsible with numbers and be willing to take calculated risks at positions. At 7 mil for BB I think it's worth the risk to stick with DB/JCT/a draft pick.