I’m making progress but taking it slow, trying desperately to not end up with something misaligned.
“Measure twice, cut once”, as they say (or in my case, “Measure as many times as you want and still cut it wrong”).
Fortunately, I snuck up on straight, true, and even. Between the circular saw and the bench sander, I eventually got there without wasting any metal stock, so that goes in the W column as far as I’m concerned.
I plan on using socket head through-bolts at the front. At the rears, I will drill the aluminum for 8mm helicoils. Likewise at the bottom, where the vertical blocks will bolt to the base plate.
The engine has to sit in one specific location where the starter motor, the bottom of the CVT plate, the spark plug cap, cylinder, and the intake/exhaust ports are all clear of the frame, and the drive sprocket aligns with the idler and rear sprocket.