Gotta chirp in on retract servos, and alternate possibilities:
I have 2 servos installed in my Top Flite Mustang ARF (1 each retract unit). The are NOT retract servos tho, they are low profile, hi torque, PROPORTIONAL servos that LOOK like retract servos. Using servos of this type has at least 2 advantages over standard retract servos:
1) they are much easier to set-up, since the endpoints can be adjusted on the transmitter, rather than having to determine exact amount of throw needed and adjusting linkages accordingly
2) the speed can be controlled (even independently) by 1 of at least 2 methods:'
a) use of a servo speed controller OR electronic cycle time reducer. These are available from several sources (including Hobby Lobby, Lado, and a site called Dionuysus' something or other), are light weight (just a few grams or less) and inexpensive ( as low as $10 each ).
b) use of servo speed control which is on SOME higher end transmitters, such as my Futaba 12FG FASST.
I can see no reason why any of those methods could not be used on this Hangar 9 bird, meaning you CAN have slow and offset retract cycle times for more realistic action. Have a look at mine:
http://www.youtube.com/watch?v=_LIFkga6lA4
BTW: mine is using stock retract units with RoboStruts installed.