Question: When assembling stair treads and risers, is it better to have the tread tucked under the riser or have the riser tucked in between the tread and the stringer riser backing? I am inclined to think the former because that way the tread gets more framing support but the way my current stairs are assembled is the latter, hence my uncertainty. 

See picture.![enter image description here](https://i.stack.imgur.com/4Me0r.jpg)

Answer: 
Treads and risers install should start at the bottom step. First the riser and then the tread. However, on the tread you leave a 1/4 inch gap on the back edge and then install the next riser. Your riser should be at least 1/2" thick and the tread no less than 1" thick. This gives support to the back of the tread and the 1/4" gap allows for expansion.
Since you probably have to rip both the tread and the riser to size, I would install a tread and then the riser on top. So the ripped edge of tread would be covered by riser and the top of the riser would be covered by the next tread.