Steering question on 1974 20ft CC SF

[fly4navy]

Just finished two test runs on my newly repowered 74' CC (115 H.P. E-TEC). All went well, engine ran smooth and quiet as cats paws.. and the scuppers are draining well (down) and keeping the water where it is supposed to be.
I noticed that the steering was free and easy up to about 15 kts and from there became progressively harder as I moved up to 25+ kts.
My E-TEC dealer, who is familiar with Seacraft suggested that I trim the engine forward, at speed, until just about when the prop breaks free, then back it down slighly. He states that this will give me easy steering and improve my overall numbers by about 10%. Says that having the engine tucked down tight to the transom is what causes the issue.

I would appreciate any comments members might have on this situation.

Thanks in advance.