[daveschroeder]

Someone privately asked me for more detail, but I was not able to respond directly by private message...here it is:

Once the bow spring is out (and it's not fastened to anything -- it's just under tension), the flap moves freely between its open and closed positions. So freely, in fact, that it will rattle if it doesn't have something holding it in a position. So basically, the zip tie (or you could use heavy wire, or similar) just goes around the whole pipe where the flap is, over the external "axle" part of the flap where the spring used to be, to hold it in the open position. It doesn't take a lot to hold it, but it takes something. There is probably a better option than a long zip tie, but it seems to be working just fine for me.