I purchased a Larson Cabrio 29 new in 2001. It has twin Volvo 4.3's . When
coming out the hole occasionally the starboard engine cavitates requiring I
back down and once again slowly bring up to speed. It may or may not happen
with identical loads and weight distribution. Yes both stern drives down to
max. I have Bennett trim tabs and yes they are down. Props? I don't know
anything about them except that they are SS.

One other issue is that I cannot trim utilizing stern drives. Any trim up
adjustment results in cavitation.

Any ideas anyone?

When
coming out the hole occasionally the starboard engine cavitates requiring
I
back down and once again slowly bring up to speed.

Swap the props and see if the problem moves to the other side? It may be
that one of the props has some unseen anomaly.
BTW, what you are describing sounds like ventilation, rather than
cavitation. My understanding of cavitation is that it occurs right at the
prop blade surface, whereas ventilation is caused by the prop sucking air
down from the surface and losing it's grip due to the air pocket.
Check to see that the drives are both going down to the same angle?
Are the drives going down far enough? Do the hydraulic cylinders retract
all the way? Equally?
Check to see if both drives are parallel? (Meaning, both pointed in the same
direction.)
A hydrofoil can prevent ventilation, if it is the "plate" type, rather than
the "wing" type. At least it did on my 20' I/O.