Updating this post for the records:
Calculations are here: https://budgetlightforum.com/t/-/41130/124 (post 124)
Inductors: (done but not decided)
The three inductors to beat, all 17.15*17.15mm: SELECTED FOOTPRINT
http://www.digikey.com/short/39nz84. IHLP-6767GZ-11 IHLP6767GZER150M11 15uH 14A rated, 12A saturation, price $5.95 each SELECTED (but the other two in this size are viable options and fit)
http://www.digikey.com/short/39nz8h PA4344NLT Series Datasheet 22uH 12A rated, 18A saturation, 26.5mOhm, price $4.55
http://www.digikey.com/short/39nz8b IHLP-6767GZ-11 IHLP6767GZER100M11 10uH 19A rated, 17A saturation, 9.3mOhm ,price $5.95 each
If you can fit 22mm on the Q8 I definitely would. You can bring 26mOhm down to 7 (BIG efficiency savings, few watts in 3.5V output ) and get a full 15A rating!
http://www.digikey.com/short/39nz8r
Caps: (done) see post: https://budgetlightforum.com/t/-/41130/132 (post 132)
1210 10uF, for input and output. Maybe include 2 or three in parallel for input, (to save about three percent loss in 14V output)
I can find some cheap ($.30)
http://www.digikey.com/short/39nzjt SELECTED. (for input and output)
and some individually specced (rare, reading through these cap sheets is a pain) up to high frequency, even if not amazingly low ESR/tan delta/dissipation factor/high Q (average).
http://www.digikey.com/short/39nzj3
Diodes: (in progress, not quite given up yet)
Things to consider, primarily Vf, and max reverse voltage, forward current, but thermal performance is also important, including reverse current at high temperature.
A number of diodes in exist in POWERDI5060-8 like this: SELECTED FOOTPRINT
http://www.digikey.com/short/39n297 SBRT20U50SLPQ
http://www.digikey.com/short/39nzj8 SBRT20U50SLPQ
http://www.digikey.com/short/39nzjz STPS30L30DJF
This one has a particularly low leakage even when very hot (Vf might be a little worse though)*:
http://www.mouser.com/search/ProductDetail.aspx?R=0virtualkey0virtualkeySTPS30M60DJF-TR
But there seems to be more selection in TO-263 (D2PAK) like this:
http://www.digikey.com/short/39n299
There are also TO-220 through hole packages like this:
http://www.digikey.com/short/39n299 (mouser has many)
Which may provide different heat sinking options.
Diode heatsinks (impact solder footprint and space):
The POWERDI5060 and D2PAK can proabably fit on the same pads if made a little cleverly and extra large pads are documented to help cooling anyway. The 2-wire To-220-2’s like the one above might be able to span the same footprint too if we really want a do-it all pad with through holes. Most of the TO-220’s are three wire though with the anode in the middle, which becomes a different issue.
*0.1A leakage current is 1.6W times duty cycle so 0.8W at 2:1 or 1.6W in 4:1) Some of these get up to that level when very hot! Not a big deal when using 84W output but keeping leakage to 30mA is better. Low reverse current seems worth probably 0.1V in Vf to put them in some balance.
MOSFET:
The trick here is rdson and gate charge divided by voltage it's measured at. Every 30 nC/10V (3 nF) produces about 0.11W of minimum switching power at 1Mhz even in low modes. Keeping this below about 6nF is very helpful, 3 is better
30mohm of Rdson however produces in the ballpark of 9W of power at 15A in 14V output, so getting this below 10mohm is very helpful, 5 would be better.
TA found this:
http://www.digikey.com/short/39nh5h
Which I think is probably fine, and the footprint seems easy to find things in, but I'l look a bit more later.
Update: gate charge is way to high.
This seems much better,
http://www.digikey.com/short/3bj1wp STL30P3LLH6
and this is probably a better compromise yet:
http://www.digikey.com/short/3bpr78 BSC084P03NS3 G (I'm liking this) SELECTED 8.4 mohm Rdson, 6nF gate capacitance.