It would have made the episode a little more interesting/suspenseful if the roadblock was after the double u-turn. I know the producers had no idea that Max/Katie, Bates/Anthony & Caroline/Jennifer would get there so far ahead of Joey/Mehgan & Mona/Beth, but the odds were high that at least one team would get an earlier flight. So unless they thought the bagpipes was going to be more of a challenge than it was for most of them, having the roadblock first and the u-turn board with the clue to the pit stop was just anti-climactic.
I know it's easier to think these things through as viewers, but it would have been nice if Bates/Anthony decided not to use the u-turn. They knew they were one of the first three teams to arrive in Edinburgh & they knew that the roadblock didn't take them very long so even though they had no idea how many clues were still hidden in the fireplaces they should have known that they were in the top three. Knowing all that the only reason to use the u-turn would be either they wanted to give Caroline/Jennifer a cushion in case they fell behind or as someone else mentioned to help Mona/Beth catch up as a thank you for helping them. Unfortunately for us, this meant that as soon as they did that we knew that it was either going to be Bates/Anthony or Max/Katie in first Caroline/Jennifer in third and Mehgan/Joey & Mona/Beth battling for last. Seeing how Bates/Anthony had a hard time moving the barrels it wasn't a stretch to see that Mehgan/Joey would struggle and probably be eliminated.
It would have been more interesting if Bates/Anthony didn't u-turn anyone and if Max/Katie u-turned Mona/Beth. Then we could have seen if Mona/Beth would have u-turned on Mehgan/Joey to save themselves (which would have been the smart thing to do).
Previous seasons have shown that there are so many things that can factor into the final leg that it's not necessarily going to be an easy win if you bring "weaker" teams with you. As we saw last season, while it's nice to win prizes it's only important to not come in last on every leg and first on the last leg when it counts.