Speed control on 737-800
Sycamore:
The speedbrake is pretty much pitch neutral, perhaps a slight pitch up tendency (according to the book).
Can be used full up to 320kts then only half until Vmo 340kts as it puts high stress over time on the tail.
Vessbot:
I am still with You on the basic theory, BUT if unable to trim NU for any reason with a out of trim ND stab on the -800 you WILL run out of elevator if power is not reduced to control speed.
So a thrust reduction for a prompt return to say 230kt pluss/ minus , then trim and return to say 70% N1 for level flight or 85 to 90 for a good climb when in better trim and better elevator effect is a must.
The 737-800 would never ever have been certified with the adverse pitch/power couple if certified as a new aircraft Type.
Quite a ride , if You get behind and out of synk with pitch and power. Proven time and again on GA with full N1 and slow trimming. ( the opposite of the above, but still not AOA or speed stable!).
Regards
Cpt B