My field is fairly small and I am a terrible terrible pilot so I'm always looking for something slow. One thing I have been doing on a lot of builds is making the wing bigger (which is the opposite of reducing weight). Most of the designs are straight forward to modify in this way by just extending the wing root with a couple straight lines. I try to be conscious of servo wire lengths when doing it, which sets how much the wing can be extended. My Tiny Trainer sport wing has a 20% wider wingspan which drops the stall speed by about 10% which then means a lower pitch prop and/or slower motor can be used. Peeling the paper off inside the wings can offset the weight added by the extra wingspan, although that is a protip for any build that already has a decently sturdy wing. Keep the paper on the control surfaces though. My FT Goblin has a 10% increased wingspan and ended up within 1g of the default build!
I'm always shocked putting these things together though. "
Let's see, the completed airframe weighs in at 150g, this is going to be so light!" then I put all the servos and electronics in and I'm over 350g again. It is amazing how fast everything adds up. I've ordered some 5g servos and a micro receiver for my future builds which alone will drop 25g from a normal 4ch build.
@Hai-Lee what's your go-to motor and prop for that lightweight slow fly configuration? I've been looking to expand my motor collection with a lower KV model and trying to find a good combination in eCalc is pretty tough.