I posted a new IR per a member request for a good clean Strat sound.
Immediately I think Fender Twin.
I setup a Helix preset and loaded the stock US Double Norm (Fender Twin) amp block and separate US Double C12N cab block.
I then copied the preset, deleted the cab, and changed the output to USB 5/6, opened AT4 and setup its Fender Twin Model, turned off the AT4 amp, then tweaked the speakers and mics to what I liked.
Processed the AT4 cab model per my post http://line6.com/support/topic/19604-irs-from-amplitube-4-cab-room/
Copied the Helix preset again and put in the new AT4 IR block, then I ABC'd the presets.
Again, the resulting IR directly in Helix is slightly different than Helix Amp into AT4 cab plug in. I actually think it sounds more open than the AT4 plug in and less nasally than the Helix cab (sorry to use that term again L6, i'll try to find a better one).
I'm also noticing that 1024 sample settings on the IR's are a bit more mid-rangy than the 2048 sample setting. Setting them to 2048 samples is almost like throwing a deep switch on an amp.
Fender Twin Cab IR
4/6/2016
Cab: Fender Twin
Speaker: American Alnico x2
Left Mic: Dynamic 57
Right Mic: Bottle 563
Room Mics: Condenser 87
Helix presets: Fender Twin IR 1024.hlx & Fender Twin IR 1024.hlx with IR in Impulse slot 27
https://www.dropbox.com/sh/009bkqzooza1aop/AADER2D9wah_GtlL5ygW7-fCa/IR/Fender%20Twin%20AmAln%20SM57%20Bottle?dl=0
I posted a pic of the AT4 screenshot of the cab setup this time and a readme.
I also posted the Helix stock preset I compared it to.