There is another thread on this someplace on Head-Fi, but in my experience, the best sleeves for the 716s are Complys (I am using the shorts), or the original foamies (black) that can be purchased from Etymotic or on ebay ($14 for 7 pair). Complys are a more rigid foam, silicone based, and really provide a great seal if you get the right size (they come in standard, slim and short). I had used shorts with my ER4Ps, and while they are relatively close to the filters, so far no early blockage. I am going to try the slims, which are longer than the shorts, but not as thick as the standards (which are just a little too thick for my ears).
Don't know about Shure tips and the IM716s. Some people jam the shure olives onto the 716s, but I found that too risky in terms of breaking the sound tubes. Plus, the olives are also short and might cause early filter failure due to being close to the filters.
Another option, also outlined somewhere on Head-Fi, is to remove the filter material, replace it with some foam, and reinstall the filters. Some people say it sounds better than the original filters, and costs nothing. Others soak the filters in hydrogen peroxide, let them dry, and re-use them. I haven't tried either, but I might down the road.