I've usually found that binder bolts aren't as tight as quick releases. However, I'm a big believer in the uses of old tubes. See if you can fit a section of old road tubing in there, in between the post and the frame, and be super careful not to drop it into your frame If you can fit this, it should work. If you do decide to go with a binder bolt, one nice thing is that you can use a section from an old mtb tube as a gunk guard. You slide the post through it when you install it, and this covers the gap between the frame and the post, so that no ooze and water get in there. Like a suspension fork boot. One of the many uses of old tubes...