So I took your advice and shot an email to Twisted Tuning a couple days after you posted. Unfortunately, they haven't emailed me back, so they likely don't have an answer to give me just like MHD. Unfortunate, but not a deal breaker.
Edit: Twisted Tuning got back to me and said that their off the shelf tunes leave all the stock trailer features intact with no modifications. Like MHD they don't have much of an answer for towing beyond trying them out myself. They did say they'd be happy to make me a custom tune for towing if I'd like, but I'm pretty sure their off the shelf stage 1+ will be fine. /edit
I can log with ProTool, so I'll just keep eye on my intake temps, knock, boost target, and trans temp. If anything starts to look abnormal or unsafe I'll just flash back to stock. I keep a cable in the X5 and MHD/XHP on my phone so it's not really a big hassle.
Realistically I don't think it will be an issue; at the very least XHP certainly won't. MHD likely won't be an issue under normal conditions either. My worry was that I picked up and hauled a project car through the mountains last year with no issues, but I'm thinking the additional boost on stage 1+ going uphill for miles on end may eventually heat-soak the intercooler. Obviously the computer should pull boost if intake temps get too hot, and even with a good load I shouldn't be sitting at peak boost all the time either.
I'm probably just worrying too much about it, but hearing some other's experiences couldn't hurt. Well, if they actually had any to share that is... In any case, I'll probably go through with the tunes, and if I have any issues I'll post up. Thanks for the input
