It seems to me the reasons the ORMA booms are shaped the way they are don't mean anything to the boat you're applying the design to.

If I understand it correctly, the flat section of the boom on such such boats serves two functions -

One is that it forms an end plate of sorts for the main. Unless the foot of the main is close to the flat section, there will be no end plate effect. The picture of your boat shows the foot of the main to be well separated from the boom. Thus no end plate effect, and your class rules may specifically not allow end plates or may calculate your sail area differently if they are used.

Two - the flat area makes a nice platform for controlling the bottom part of the main when reefing. Again, I don't think this applies to your boat.

I'd go for a carbon tube with the appropriate main traveler built onto it. As there are no benefits of the t-section for your boat, I'd think it would only get in the way, add windage, and hurt like hell when you hit your head on it.

But I could be wrong...