A big thank you to John63 and Scottthewolf -- for your advice on the Whirlpools.
As I confirmed directly with Whirlpool the specs on their blower motor is 230 CFM (far more than any booster fans I looked at -- even though none would work for me in my situation).
Today we confirmed through the 1st load of clothes -- the dryer works and works well.
An average sized load dryed in approximately 38 minutes!!!
What a difference between this Whirlpool and the LG (which would only fire for 3 seconds before shutting off). I suspect their blower motors are equally as weak as the Samsung (125 CFM) but LG refused to provide this information to me.
What I will say is that the LG is all about flash & dash -- it definitely looks a bit sexier than the Duets, mounts much nicer/more securely with their stacking kit (the Whirlpools only have a mount bracket in the rear and they use a crummy rubber strip which mounts on the outer edges of the washer -- and which is used to set the dryer and presumably prevent metal-on-metal movement/contact. But not nearly as secure or as nice looking as the LG.
However, none of that matters when the LG simply doesn't work.
So please, take John's and Scott's advice if you have a long dryer vent run -- do yourself a favor and get the Whirlpools because they DO WORK!
Many thanks guys!