I see in the charts that you published for B"B 29b that you understood that Rashbam has 3 opinions on how a non-consecutive chazaka on a slave maid works when there is a partnership contract between the partners for the working arrangement.
I think that Rashbam only presents 2 opinions.
1. If there is a partnership working arrangement document the chazaka is established immediatley.
2. Chazaka is established after 3 years; in a combination of partner A extracting usage 2 years and partner B extracting usage of 1 year.
I think the proper reading in the Rashbam's second opinion is with a comma after "m'fizarot. ״כיוון דאיכא תרתי שני חזקה מפוזורות, ועיטרא...״. Not with a comma after "tarti".
And after that the Rashbam with ״ואין נראה לי כלל״ is coming to reject his first opinion that the chazaka is established immediatley in the case that the partners memorialized their working agreement in a itra document.
Jacob Weber, N.Y.C - USA
a) I found, bs'd, in Chidushei Rav Baruch Sorotzkin zt'l (by the Rosh Yeshiva of Telz, Cleveland) on Maseches Bava Basra, page 392, DH v'Nir'eh (available on Otzar ha'Chochmah), that he explains that the Rashbam does not mean to say that there are two scattered years of Chazakah, as the simple reading of the Rashbam's words would suggest. Instead, the Rashbam means that there are תרתי - two matters. These 2 matters are:
1) Scattered years of Chazakah
2) Itra
Rav Sorotzkin writes that if the Rashbam would have wanted to say that there are two scattered years, not two matters, he would have written תרי שני חזקה .
The word תרתי does not mean two years; it means two things.
Rav Sorotzkin learned that the comma belongs between תרתי and שני חזקה and it indicates that two does not refer to the amount of years.
b) Comments on your Pshat:
If אין נראה לי כלל of the Rashbam is coming to reject his first opinion, then why did the Rashbam not make this challenge immediately after he mentioned the first Pshat? He should have written אין נראה לי כלל before he wrote אי נמי because that way it would have been clear that he is coming straight away to reject the first opinion. The way he wrote it suggests that he is challenging the אי נמי explanation that he cited immediately before.
If we are understanding that the words in the Rashbam תרתי שני חזקה מפוזרות to mean "two scattered years of Chazakah" then where is "partner B extracting 1 year of usage," that you write, mentioned? Only two years are mentioned in the Rashbam. not three.
c) The source for the meaning of תרתי:
I think it is worth noting a source for Rav Sorotzkin, that I cited above, that תרתי means "two matters."
We find an example in Gitin 23b where Rav Shmuel bar Yehudah said in the name of Rebbi Yochanan תרתי.
Rashi (DH Rebbi Yochanan) writes that he said one thing about a woman's Get and another thing as well.
We note that the Gemara there did not use the word תרי instead of תרתי since this would not indicate two matters.
d) Explanation of Rashi (29b, DH Itra):
I am now, bs'd, going to go through Rashi and explain how we learn that he cites three opinions, that:
-according to the first opinion Chazakah applies immediately;
-according to the second opinion Chazakah apples only after 6 years;
-according to the third opinion Chazakah applies after 3 years.
1) Rashi writes explicitly that Chazakah applies immediately according to the first opinion.
2) אי נמי is the second opinion. We learned that תרתי means two matters, not two years. According to this, there are שני חזקה מפוזרות -- "scattered years of Chazakah." One owner had years 1-3-5 and the other owner had years 2-4-6. The years are "scattered" between the two owners. They are 6 years that are scattered between the two owners.
This is written explicitly by one of the Rishonim, the Tosfos Rid, who writes:
ומדקאמר שני חזקה מפוזרות משמע דבשש שנים קאמר דאיכא לכל חד שני חזקה מפוזרות.
Each of the two partners has scattered years of Chazakah. This means that each one has 3 years which comes to a total of 6 years.
3) Rashi then writes that the second opinion does not appear to him at all to be correct, but rather the first 3 years represent a Chazakah. (This suggests that according to the second opinion, 3 years was not enough for a Chazakah.)
Dovid Bloom