Hi, I have a problem with my Giant U-Can-Do 3D. The nature of the problem is such that I can't really get it fixed by T&E.
We have a fairly short runway and somewhat steep approaches are needed to get down there.
So I land my UCD using crow 'mix' (both ailerons fully up, and both flaps fully down, delayed 20deg down elevator).
Flipping the switch on the downwind leg at about 1/3 speed works very well, the plane doesn't pitch in any direction
it just slows down to a crawl...need about 1/3 throttle to keep it flying!

The problem comes on final where the speed gets even lower. The plane then starts pitching up and down,
and its so bad that it is 'unsafe'...and certainly uncomfortable. Feels exactly like flying with CG WAY too far back.
The result of this is that the plane either 'crash' into the runway (or in the high grass before the threshold), OR I have
to make a go-around. Have straightened the landing gear too many times, and broken too many propellers now.

Can't quite wrap my head around this...
--The CG IS right,
--I don't think I'm flying in & out of stall (but maybe I am?)...
The other pilots are amazed that this plane comes in so slow that one
could actually run alongside it...in dead calm wind...and the plane is even a tad heavy at 14.5lb (gasser + strengthened LG area).
--Maybe the crow mix is shifting the center of lift forward on the wing, requiring the CG to be moved forward also in order to maintain balance??

The last attempts at fixing this has resulted in broken prop and some 45deg camber on the main wheels after each 'landing'...

I probably will not fly again until I have a better understanding of whats going on.
I need the crow mix, and I also WANT to use it, even if it wasn't needed.

Any ideas?

Why not just use Spoilerons, which would pitch the nose up and allow a steep, controlled descent? Hit them on final and use the throttle to control descent, increasing it just before touchdown. That's what we used to do in competition funfly. It just might do the trick....

Any problems with flicker / tipstall in that configuration ?

I fly sailplanes with flaps and land using "crow". Crow makes the plane super stable and tip stall resistant - the wing root is at a much higher angle of attack than the tip so tip stall won't happen. We find that raising the ailerons helps slow the plane some and reduces lift but makes the ailerons less effective for roll control. I don't reflex the ailerons for landing on my planes any more.
I have a UCD 46 and fly with a guy with a UCD 60. I would absolutely not mess with flaps, crow, etc to land a plane like that, no matter how short the field. If other guys can land any sort of sport planes or trainer on the field you can easily land a UCD . It will land at very low airspeed. Come in low and slow with low power, about 1 foot off the land reduce power and raise the nose and settle down. They slow very quickly at idle and high angle of attack. This is a 3D plane for heavens sake. You can harrier it in when you get good enough.
In a slight breeze we land with no roll at all.

I'm with AeroDave on this one,just use up spoilerons. How much is up to you. I had one plane with split flaps/ailerons and never found much use for crow(this is not a sail plane with small surfaces) I used spoilerons(full span) for windy days when the Do tended to keep on flying or jump 5-10 feet straight up in a gust. Also, a tail heavy plane will "sink" more predictably with spoilerons. I used to be able to head straight down,low throttle until it almost hit the ground and then pull up to a slow landing without any speed build up with spoilerons,I have seen another guy do it with crow but I dont know how he worked it all out,it didnt work well for me. If you have a Futaba 9C,you can do the craziest mixing that is available.(or 8U for that matter). One thing I had to do with that mix was link the spoilerons to elevator. I had them set up to go up with Switch C,but if I pulled up elevator,they would come down in a linear mode with the elevator motion. I did this because on the final approach the plane would drop too much even with up elevator(wing is always loosing lift)and would hit pretty hard. When I mixed in the elevator, when I flared to land,spoilerons dropped and wing regained lift and the plane landed normally. I also used to open up another set of P-mixes and add in throttle-Spoilerons,set offset to about 1/3-1/2 throttle,then if I had to throttle up suddenly(bail out of something) the spoilerons would also drop to neutral in that situation too. I dont think the Giant Do will allow the latter,it would require 3 more P-mixes I think,not sure if you would have enough. Any way the spoilerons alone are effective as air-brakes IMO.

Ok. I'll try out some of your suggestions as soon as the new propellers arrive.

Steep approach+ short runway= sideslip?
Just a thought.

Forgot to mention that its best to mix throttle to any crow/airbrake/spoileron where moderate to high throws are used,that way if you hit the switch by mistake,at least at higher throttle,the mix will not deploy.