Apologies to those who leave comments as I only remember to check the post now and again. I've published the comments that came through the letterbox now.
One thing has been bothering me about the experimental lectionary. In Sarum there was a custom of celebrating the "Little Office" of St Mary on ferias in addition to the ferial office: it was said rather than sung. But on certain days the Plenum Servitium or full office of Blessed Mary was sung instead of the ferial office. Sarum specifies certain days when this should take place: the Tuesday before Ascension - Rogation Tuesday that is - and the Friday before Whitsunday are two such days. It also seems fairly clear from the rubrics that the Plenum Servitium was meant to be said on Saturdays in Advent. The Breviary gives a specific office of St Mary for use in Advent; and one for use outside Advent with a special Eastertide variation. Because the lectionary I am building is so tight, so full of continuous series of lessons, there is little wriggle room to fit in this kind of variation. I therefore built it into Advent and the other days mentioned above. I think, though, that for the rest of the year, I should allow an option for the Plenum Servitium in the lectionary on at least one Saturday per month. The Sarum Breviary provides six different sets of lessons for the Matins of Blessed Virgin throughout the year outside Advent and Eastertide: it would be good to use them all.