Hey Rob AKA "Blisster" ... Welcome to the "Do" World ..
With the planes that you listed, You should have no problem flying the "Do" She's a
real floater, and lands really easy.. As you said she is no speed plane... It's also good
that she lands easy, because you are right on the gear, it is a weak spot... The least
that you should do is to add more epoxy, with bulsa strips from the block up the sides
to about where the bottom of the tank bulk head...
Or you can use the "gjeffers " method, which is what I did on "Do" # 2.... From the wing
opening on the fuse, look for the wood dowls(reference) that goes through the L. G. block
look to see where the L.G. blind nut are, Then drill a hole(2) slightly smaller than a 4-40
rod stright through the middle of the landing gear block from the wing opening, to the
exhaust exit behind the firewall area, cut 4-40 rod to fit and epoxy in.... It works great
and it's real easy to do. The 50SX should do OK, as you read, most use the Saito 82
(which does great in the "Do") on up to the "gjeffers power hungry" Saito 100 I',m
using the S-82, I had a YS 63 and the Saito 100 in "Do" # 1 Both worked Great!! With
the 100, 1/8 to 1/4 stick is all that you need

I use tailwires, but they aren't needed as long as you DO NOT SCORE THE BULSA "IN
ANYWAY" when removing the covering for the area to be glued to the fuse... There's
different methods to do this... The way I do mine... I mark the stab, then I lightly cut
the covering down the center of the marks,( IMO, cut not as critical, because it;ll be
covered with epoxy and it's in the center of the fuse) then work the covering up from
the cut and peel it back to where I'm going to cut it, fold the covering over and with
just the blade of my knife laying flat slide it down the fold, iron the ends and 30min
epoxy the stab in...

Your servo's mentioned should be good, I use HS 425bb(57oz) for all but the rudder which
has a HS 645mg(I forget, but plenty enough) I do run on 6v's IMO... I think 50+ oz on "ALL"
the surfaces is plenty, since you can't really use full rudder on the "Do" "to much coupling"

The "Do" is built light, She will not take much abuse..... But she's a great floater, lander and
all around fun plane, She does a lot of things well, inverted flat spin is one, hovers all day if
it's powered right, and somethings not as good..... But for me The "Do" is King of fun!!!

Have fun and keep us updated on your progress!!