3 SP*s, 2 SPs?? Hmm ...

Is it possible to start three pitchers with the SP* designation and then rotate two non-* SPs in the fourth spot? Has anyone tried this?

Couldn't find much on this in a quick search ...

Yes.
SP* in the rotation at 1-2-3.

With only 3 in the default rotation, you can leave it alone and HAL will put the most expensive SP in the 4th spot, and then the other SP when he's the only available SP based on rest.
If one of the SPs is SP/RP, you can leave them out of the default rotation and HAL might use them in relief.

Yes! We did this in a 1935-1949 league, it was great fun. A few extra bucks in the pot for your additional pitcher, it was nice to have some of the non-* SP's take centerstage.
The teams police their own teams, no mor than 3 * on a roster at once. Commissioner (That was me...) routinely pulls rosters and reviews.
The star pitcher for the champs was '46 Schoolboy Rowe with two playoff shutouts. You guys ever start a 3 * league, let me know. It was my fave format.
peterc1956

This is fun, thanks! Appreciate you sharing your experiences

Well, good to hear! As for me, I enjoyed having 3 RSP and 2-3 LHSP that I could schedule for different ballparks and opposing lineups. Was far more interesting to set my Starters up for each series!

https://365.strat-o-matic.com/team/1726109

Different take here my ace was a 5 day starter and 3 middle of the rotation guys and a #5
https://365.strat-o-matic.com/team/1681957

That's the ticket!!

Currently tops in an $80m league with a 6-man starting rotation: 3 SP*, 1 SP, and an extreme righty and extreme lefty as streaming swingers, who also double as RH and LH bullpen specialists.

https://365.strat-o-matic.com/team/1726414

This strategy was born of my complete aversion to a 5th SP in the Four Aces strategy who never pitches, except to come in and lose an extra-inning game for you.

Currently tops in an $80m league with a 6-man starting rotation: 3 SP*, 1 SP, and an extreme righty and extreme lefty as streaming swingers, who also double as RH and LH bullpen specialists.

https://365.strat-o-matic.com/team/1726414

This strategy was born of my complete aversion to a 5th SP in the Four Aces strategy who never pitches, except to come in and lose an extra-inning game for you.

I've done something similar in the past, and on my sheet for the draft:
SP1
SP2
SP3
SPA
SPL
SPR

It's possible that only makes sense to me

I've found that something like this can work pretty well in 2021, 2022: 4 starters who usually go every fifth day, with one extreme lefty and one extreme righty to use as the fifth starter, depending upon the opponent's splits (e.g., https://365.strat-o-matic.com/team/1721532). But for me it's worked less well in ATG, because of the ready availability of good platoons among the huge number of available hitters.