I've done some basic maths related to the V4 numbers as shown here.
View: https://x.com/elonmusk/status/1960812698037518540/photo/1
Starting from the stages propellant masses given
4050*110% = 4455 (because a 10% propellant mass fraction that is: 0.90 : 90% of props, 10% of rocket )
2300*110% = 2530 (because a 10% propellant mass fraction that is 0.90 : 90% of props, 10% of rocket)
Raptor isp : 340 seconds (ground) and 370 seconds (vacuum)
And thus...
9.81*340*ln((4455+2530+200)/(445.5+2530+200))+9.81*370*ln((2530+200)/(253+200))
= 9243 m/s with 200 mt of payload.
Both stages with 0.90 propellant mass fraction.
As a matter of fact, Falcon 9 stages are in a 0.94 (if not a 0.96) prop mass fraction ballpark. Which matches the all time record: Titan II first stage, also 0.96 in the early 1960's. Titan I booster stage was already 0.94, dropping the LOX cryogen for dense storables helped - and then Martin Marietta trimmed the stage weight like crazy, up to drilling holes wherever it was possible.
Bottom line: if both stages are 0.90 or better, then 200 mt + is feasible for Starship V4. One could try (for example) 0.92 or 0.94 PMF for V4, or calculating payloads for V3.
The rocket equation is unforgiving and propellant mass fraction is a b*tch.