RE: Elder 40 electric conversion
Oh man, you shouldn't bait me with phrases like "don't worry too much about insulting my intelligence." The way I feel today I might be tempted to let fly. Must... Bite... Tongue... OW!
The AXi 4120/14 on 12, 14, or 16 cells with a 14x8, 13x8 or 12x8 prop (respectively) makes a good all-around .40-size power combination, IMHO. Choose 12 cells and a 14x8 prop for sedate flying like your Elder, or a Piper Cub. Choose 14 cells and a 13x8 for general .40-size sport models. Aerobatic models and "heavy metal" warbirds benefit from 16 cells and a 12x8 prop.
What's nice about the AXi is that there are no gears to strip or pop loose on a bouncy landing (you know who you are). While the motor itself is less efficient than a conventional brushless capable of handling a similar amount of power, overall, it's a wash because you end up adding a gearbox to the conventional motor.