I have built three aces,in two sizes,including one the same as yours.As pointed out by others this is a very good first "build from plans" project(no way Im getting into the definition of scratch building!),since the fuse is a simple box,and the wings flat bottomed and constant chord.I use the two template method of making constant chord ribs,and it works well.I used a ST .90 on mine,which was a perfect match.If I built another in this size I,d use a 1.20 4 stroke.
A few suggestions: Dont fool with the soldered wire LG.Suggest you find a formed aluminum one of approx the same dimensions .Check the SIG catalog.
Cut the fuse off at the firewall and mount the engine sideways.Make yourself a fibreglass cowl using a foam plug.This way you sidestep fuel soaking into the wood cowl,and the whole model looks much better IMO.
Consider scrapping the wire cabane structure.I did on my last "BIG" Ace ,repalcing it with an ultimate single beam setup supported by four aluminum uprights.Much stronger,cleaner,and no solder joints to look after.
As long as you get the CG in the right place,and the incidence of the wings correct ,this will be one of the most delightful models you will ever fly.
Incidentally try to keep the weight under control.Mine balanced without ballast,with the servos in the standard place.Id use your favorite iron on plastic for the wings,and fabric and paint on the fuse........
All above IMO,and my $C.01 worth........

For clarification there are kits or plans,avail for four sizes of ACE I beleive,and the one you are building is the original,which was detailed in RCM,years ago.
By the way,if you try an outside loop,do it at least 3 accidents in altitude,cause that flat bottomed airfoil doesnt seem to want to tuck under.at the bottom of the loop.......