Been flying a FiveJet for 3 years now, and could not have had a better introduction to jets.
I have a MW54 mk1 manual start , dubro 50oz tank, flaps, Spring air HD, balsa tailbooms with
foam/balsa airfoiled tail surfaces. Finish is glass+ water based poly, and spray can paint.
Dry weight is as low as 11 Ibs.
I have the pump and all the Nicads in the nose to balance it, but with the lighter engine
you could do away with Lipo packs, and save some weight.
Plastic film could also save some.
If you choose to build your own wing and booms, select light foam and balsa and try to save
weight everywhere from the start
The way my fuse was moulded is not up to modern lightweight standards.
It is polyester and boat type rovings, but apart from that it is very well made.
Dont think of wheel brakes and oleo legs.
Go with flaps, unless you have a mile of runway, and a constant headwind:-)
See some pics and description in Norwegian at
http://home.no.net/larsstef/jet/ go to the link "Fly"

Regards

Lars