My worry is that while I am clear on the risks (extended timeline to get a tenant in, and expensive buildout) that I am not being nearly conservative enough - do I risk this thing sitting empty for a year, or years, and finally renting well below my implied rate? 

If you achieve the ideal BRRRR with zero costs, you might as well perform it in a high PSF location (as high as you can tackle with conservative reserves).My last rehab was on a property that was almost $2k psf.  

I'd never go to Detroit unless I'm going to Canada, nothing against the folks up there, but I doubt if they'd come here too, meaning I wouldn't buy there either.I'm probably the most conservative of the bunch here, I don't mind taking whatever so long as I know what I'm getting.

.: BRRRR have some items that flips do not (plus most of the flip items):- refi appraisals in my market are conservative.  

It depends on the lender but at a min they must follow TX SML or lending laws in the state in order to compliantly lend in TX, on whether choose to apply this guideline to all types of occupancies or transaction types (non owner investment, second homes/primary residences, etc)80-85LTV on rental properties is only on the purchase for fannie/freddie loans but on rate term refinances its max 80% and cash out max 75% for 1 unit and up to 70% for 2-4 unit cash out conventional.On HELOC's and rentals are up to 70-75% depending on the HELOC investor or product.Its good to distinguish between what the lenders are willing to do and for which product and also these loan products must abide my state law as well as an additiona layer of "overlays," on top as well (whichever is worst / most conservative).

The software is going to be very conservative with your write-offs.

Also, try to find similar rental units in the same neighborhood to compare to so you have more of a rent range/conservative approach. 

From there, it's a comfortable drive on the highway, which will take you a conservative maximum of 2 hours door to door.

Recessions have a good way of making anyone's conservative assumptions look not conservative enough.  

When I do it for me and my clients, we go very conservative to give better expectations of the transition process, than if it goes better, great!