Incidentally, In all this reading on the Eucharist I have gotten quite the dialectical experience. I started with Thomas. But in the Leonine edition the text of Thomas is accompanied by that of Cajetan's commentary, most of which is simply an attack on Scotus and Durandus. Moving to Scotus, however, one finds that his text is printed next to 16th or 17th century commentaries, who spend a lot of time attacking Cajetan and the Thomists. So it makes for exciting reading.
In any case, here is what Scotus says about the Trinity.
Ordinatio IV d. 12 q. 2 (Wadding XVII 574-5):