Having no practical experience with either the Brodak Thunderbird, nor the Brodak 40, I would tend to judge the Thunderbird as being a bit larger than I'd be comfortable with, for a Fox 35. I'm sure it could be done, but it wouldn't leave much of a margin for error, like a slightly heavy finish or like Bill said, a windy day. I'd expect the Brodak 40 would probably be a better choice as it would allow for that margin. Personally, any time I look at a classic model with over 550 square inches, I start thinking ST 46, but that's just my preference.