Other Rishonom asked kashios on Rabbeinu Tam. Reb Moshe held that the kashos are so strong, and Rabbeinu Tam is so shvere, that his shitta is mufrach and not to be relied upon for p’sak. Avnei Nezer held nit azoi. It was Reb Moshe’s opinion!
Ve’adaraba, if the questions on the Ran were not so strong, I would not say it is a shvere shitta — because what’s so shvere? The kashios are not so, so strong. It is another deyah. Just because the kashios are so shtark, I said what I said.
Against Rav Papa – no. Against a Rishon — Achronim do that.