BTW, what is the standard method of adding a couple of degrees of downthrust to a model engine? Do people angle down the entire mount (with, for example, a couple of a washers on the top mounting bolts) or do you tip th engine forward by add a couple of washers to the rear two engine bolts?

I'm tempted to leave the engine at neutral unless I find there is a problem I can't solve with the tail incidence. On the wing incidence, I'm just going to stick with the scale incidence for this scale airfoil -- and assume the designers had it right to start with (and to heck with any scale effects).