I have
New 2019 Crestliner 240 Rally DX Tritoon
27" tubes Huge Strakes on all but outer edge of outter tubes
Center tube is full length actually 16" longer than outer tubes
2019 merc 200 4stroke DTS 20" shaft set low as it will go.
Can trim boat and bring bow up a good amount before props cavitate

Tested both on same day, smooth water, low wind, approx 50 gallons of fuel
Only me on the boat no gear.

Props I have tried
Merc Black Max 15.5"x15
5600 rpm 38mph

Solas Amita 14.8x17
5500 rpm 39mph

Both props seemed to run similar though the solas felt better out of the hole.

I have a merc/quicksilver Black Diamond 14.5x19 ordered
should be here today.

Should I try to stay over 15" diameter?

Any thoughts, Id like to get prop dialed in before buying a nice stainless
Looking for a fast prop for light loads on boat to run across the larger lakes.