When I bought my first inline and looking at scopes the sales guy said the same thing and steered me to a low end scope. Like usual I never listened it just didn't make sense to me to shell out the expense, time and effort to put el cheapo on top of a hunting rifle that may cause me grieve when I needed it most. As such now having bought a few inlines and scoped them all, I have yet to see a problem with scoping it with what I wanted. On the range I have protected the bottom with homemade things such as mole skin, leather, tape, etc and now have invested in a scope cover. Face it this is where it sees the most repetitive action. Before in the field I never worried about as it was usually only a shot and the residue left would easily wipe away.

I am not saying buy the best scope made just buy what ever you want for your usage/budget. In my case my ML is used as much as my CF now in regards to hunting, so to me it as important to top it with good optics. Like Triple 7 has stated ways to make sure it doesn't marr your scope bottom so don't let that cloud the process any.

As to eye relief that is really personal, I personally feel the recoil to be more of a push then CF which is a jolt so even having a 3" ER scope on my inline for 4 years it never caused me any grief. As such I have only ever used rifle scopes on my ml's but many suggest 3.5-4" as a general rule or look to shotgun scopes which afford higher eye relief. You should be able to get the specs on any scope of interest either on the manufacturer's or sellers site.