Question #2: [Rashi] explained Rava's [answer] that if [the spits] ran along the length, he puts [the Kosher Sechach] widthwise, and there is more Kosher Sechach;

In Sukah (9b), a Mishnah teaches that if one makes his Sukah under a tree, if there was more Sechach, or he cut [the branches], it is Kosher. The Gemara establishes this when he banged them down, and Rashi explained that he mixed [the branches with the Sechach], and it is not recognized which is Pasul [Sechach] and which is Kosher. (Maharam - this shows that Pasul Sechach is Batel to Kosher only when they are mixed, and it is not recognized. Without Bitul, the Kosher Sechach on top of the spits does not help! Maharam did not explain why this is not difficult for Tosfos. In Tosfos (Sukah 15b DH v'Ha, according to the Maharsha), R. Tam says that R. Ami and Rava permit Parutz k'Omed, therefore they do not require Bitul.)

Question #3: It is difficult that the Amora'im conclude like the opinion that Parutz k'Omed is forbidden, for we do not hold like this!

Question #4: Below, when we establish that there is extra room regarding a caravan, [the Gemara] does not ask "it is possible to be exact!" There, we could not answer for Rava like here!

Alternative text and Explanation #2: R. Chananel's text says "it is impossible to be exact", that he will close all the air [with Kosher Sechach], and it turns out that the Kosher Sechach is not more than the air and Pasul Sechach, and it is not even equal to it. The question is against everyone;

R. Ami answered that he put more. Surely he will close all the air.

Rava said, you can even say that he does not put more. If [the spits] ran along the length, he puts [the Kosher Sechach] widthwise, and then all the air is closed.

Implied suggestion: Perhaps Rava says that only like this helps, but not to put more, for he decrees lest one not put more!

Rejection: In all Seforim, the text in Sukah (15b) is "Rava said, you can even say that he does not put more."

Assertion: The text does not say "Ad Arba Amos."

Implied question: The Gemara could have asked about the Seifa itself!

It is unlike Rabanan, like the Gemara says, since a plank of three Tefachim does not permit opposite itself;

It is also unlike R. Shimon ben Gamliel, since it says that there may not be between one [plank] and another like the width of the plank. According to R. Shimon ben Gamliel, even more than its width is not a problem. Since there is not four [Tefachim], it is like Lavud!

Answer: This is the Gemara's style. It initially asks from the Reisha as much as it can.

Support: We find like this in Shabbos (39b) regarding hot water heated on Shabbos. (The Reisha discusses an episode in Tiverya. The Gemara inferred that it cannot discuss bathing the whole body, rather, only the face, hands and feet, and then asked from the Seifa. It could have directly asked that the Seifa cannot discuss either of these!)

Implied question: Here we hold like Parutz k'Omed is permitted. In Chulin (29a) we conclude according to everyone that half-half is not like the majority, and we bring the case of an oven [divided in half], and here we do not bring it!

Answer: Perhaps we can distinguish between walls, and Isur and Tum'ah. (Only for walls, half is like the majority.)

Explanation: [Omed Merubah Al ha'Parutz from two directions, i.e. the closed space on both sides of the breach, together they exceed the breach] is not considered Omed, because the air from this side and that side is Mevatel the top. (Even though the top two ropes are Lavud, i.e. within three Tefachim of each other, this area is not considered closed, because there is a greater width of air below them and above them.)

Question (ha'Sar mi'Kutzi): Still, we should make a gap of [Mashehu] less than three [Tefachim above the ground], a rope Mashehu, a gap of [Mashehu] less than three and a half, a rope Mashehu, a gap of less than three and a half, and a rope half a Tefach and Mashehu. Why must the total thickness of the ropes exceed a Tefach?

Answer: Perhaps [if we permit] in such a way, people will come to err.