Here's some other observations though:
yeah, the bar dar is a bit of an annoying tip off (it's so precise at the sector boundaries), but you know what? You can max that sucker out and people still won't scramble. You can pork a field's fuel, and sure, someone with brains will see that and a maxed dar bar 50 miles out, and start yelling on channel 2 "HQ Attack inbound!", but nobody will come. The ONLY time I've seen massive numbers repel an HQ attack was after they show up on radar as dots.
Ultimately, you've probably got an overkill situation. If it only takes 2 B17 forms to guarantee destruction of the HQ, you can probably fly those in and drop before being intercepted. If you take 12 B17 forms there, everybody who sees the blob inbound will be up in a komet.
Incidentally, we're looking at prime arado material here. Send some norden aces ahead in Ar-234s, and have them pave a path through the radar. Ar-234s are great for prestrike prep. I remember hooking up with a couple guys and flying a single Ar-234 for 4-hours -- climbout, go on station, liaise with a strike as it rolls, whack the field radar and fuel 10 minutes before the props arrive, land, rearm, repeat.