I haven't been around for a while, but here are some of our numbers from the Power thread regarding the MXS, and several contributors made this happen.
Since the question was about the gas versions, I'll limit the info to gas setups, but I will say that the electric version (3183g or 7.02 lbs) is just 3.5 ounces heavier than the electric version of the 78 Extra 300 (3083g 6.80 lbs).
The gas version of the MXS is 3527g or 7.78 lbs, so you can use your own components to get your estimated AUW, but here would be mine:
First, since I know the weight of my pushrods and ball links, and hardware, which are slightly different than the ones that come in the box, I subtract the hardware pack weight, which gives me 3282g or 7.24 pounds, or about 116 ounces to round it off, and I'll add the control horns and hinges separately at the end.
I can then add my five control surface servos and screws, SWB half and full arms, pushrods, pull-pull hardware, and my throttle servo, arm and pushrod, and all my JR HD extensions, which adds another 16.79 ounces. So far, 132.79 oz.
I can then add my AR 9 channel Powersafe, satellites, 2x 2S 2100mAh Lipos, an IBEC, and my soft and hard switches, and add another 6.46 ounces, which brings us to 139.25 oz for the airplane and the control system.
I can then add the intended DA-50 on a Pitts muffler:
Let's first add some standard stuff that will be the same for any setup just to keep things even, and you can reduce the weight by whatever savings your components will provide:
2.5 inch standard standoffs are 4.06 oz. I use something else that can reduce this in half, but let's stay with it anyway.
The larger 50cc Pitts is 7.85 oz with hardware. My 3.5 inch CF spinner is 2.08 ounces and my 23x8 Xoar is 3.9 ounces. I have a standard 500cc tanks with stoppers and tubing that is about 2.4 oz. Add another 20.29 oz, and that beings us to 159.54 oz so far.
Now for the engines without exhaust since we've already figured the Pitts:
A DA-50 with the spark plug, the prop hardware, and the ignition module, is 51.95 oz. This is about right because most guys will see 3.75 pounds or 60 ounces with the stock muffler (5.2 oz) and standoffs.
So add the DA-50 all-up with the Pitts, and we get 211.49 oz, or 13.22 pounds. Add about 16 oz of fuel, and we have a takeoff weight of 14.22 pounds. Now if I add the rest of the screws, hinges, and control horns, and add about 2.5 ounces for fuel proofing, we're right at 233 oz or 14.57 pounds, RTF with a full 500cc tank of fuel.
Add decals and other bling, and add more weight. If you are using a third battery for the ignition instead of an IBEC, add 3.5 oz, and if you are still using 3x 2S 2100mAh A123 batts, then this thing can easily come in at 15.25 pounds RTF.