The Summar doesn't hit the shutter on the P, 7, and 7s. Well, it sure doesn't threaten the shutter on my 7s. It doesn't go in nearly as far as an Elmar, anyways.
Like an Elmar, it can scrape along the light baffle at the top of the crate. This happens if one of the three locking lugs on the tube is pointing up. If you turn it just enough to unlock the lugs, and then push it in, it won't scrape, as there will be lugs at 10, 2, and 6 O'clock.
This lug scraping problem is only a problem with the 50mm Elmar and Summar lenses. It also happens with the 50/3.5 Serenar, being an Elmar clone. The Summitar and Summicron lenses have the groove and ball-bearing arrangement, which ensures that the three lugs are always at 10, 2, and 6 when collapsing.