Well, I've done four of them and there is a way to avoid connecting, but I don't recall the magic handshake and can confirm it's a total nightmare to go through this each time. Anything that works is fine.
I see that you've found the correct signed image on the dangowrt github. For people wondering if this is kosher, yes, Daniel Golle is one of the OpenWrt core devs and those images are from a very reputable source (he's @daniel here on the forums; for more, go scan the E8450/RT3200 megathread: Belkin RT3200/Linksys E8450 WiFi AX discussion ).