If that short turn is close to the valve, IMHO as a total amateur porter I think you'd possibly aggravate an already iffy flow condition by increasing the valve size.
If 'just' increasing the valve diameter and incorporating a machine throat opening below the seat angles into the casting, then generally yes. But again generally if one is incurring the effort to increase the valve size and this is with performance in mind some sum of porting/blending is involved which mitigates the negative, with the limitation then becoming based on the effort and capability of the individual, and/or the castings' capacity.
The tongues raise the floor and give the air a better shot at the valve which would make the port work better for the larger valve area.
Well, maybe; and it all sounds good, but it just doesn't always work that way. Remember, the goal in port modification is to provide a greater effect of coercing vs. forcing the air to follow the path set forth by the port pathway, and sometimes this requires an influence upon the air column ahead of the the intended action so as not to grossly upset the continuity in that column in the greater ulltimate intent.
As an example, though somewhat removed, and yes there are many influences at work, but just for thought: For the most part, in time, a winding river will generally increase the arc of of it's turns, the river moving outward and exaggerating the radiuses (O.K. radii
; and so remember one doesn't want to purchase the property "on the river" on the outside of a turn!
); and haven't you always been taught that "water will follow in the path of least resistance"?
Scott.