A few corrections:
Their 343 line standard was 2.25MHz. From the "TEST INSTRUCTIONS FOR THE R.F. ALIGNMENT OF THE RC-199 TELEVISION RECEIVER" document attached.
The resolution was 1.5MHz not 2.5MHz as listed and graphed in the "HIGH DEFINITION TELEVISION RECEIVER NINE INCH MIRROR LID CONSOLE TYPE RR-359" manual. A copy of my manual can be found here:
https://www.earlytelevision.org/pdf/...359_manual.pdf
Dr Kell devised the "Kell Factor" in 1934 well before the design of these sets so it was in use when these sets were designed. The RR-359A's have a Kell Factor of about 0.6.
The vid/aud spacing was changed to 4.5MHz in 1937 when the sets were upgraded to the 12" RR-359B's. All the video IF's and mixer were swapped out for the "B" upgrade per the "CHANGE FOR CONVERTING RC-199 TO RC-199B" engineering document. This doc also outlines various component value changes throughout the chassis.
No changes to the horizontal sweep needed to be made. They run efficiently from 240 to 625 lines with full width and good linearity.
All pre-war television run fairly well on FM audio using slope detection. RCA put out a letter to all registered owners after the change in 1941 that they would align their sets for slope detection at no cost.