I think I've met one of your mates Caterpillar. I saw him in Tryon the other day and he was riding a modded MIT V8 with color combo of Red & Black. You can see the bike has been through a lot. He has really pushed that bike. If I recall, he has at least 4,000km on that bike.
Some of the mods he made made use of Brompton accessories like the L fender and the Front carrier block. He uses an S Bag. Some things he mentioned was that there was chain rub in the chainstays and he had to put a spacer in the bottom bracket. He also put some sort of clamp in the handlebar post to improve stiffness he says. Lastly, he complained that the rear fender seems to be interfering with the rear wheel. He was having his wheel respoked.
Anyway, I find it quite impressive how the folding bike market has grew. Back in 2009, I viewed folding bikes as unreliable. The only ones available were in Toby's sport shops and they were pretty hard to handle. Nowadays, for even less money, you can get better quality folding bikes. How things have changed.