I purchased XL slopers sets 1 & 2 for my 45 deg home wall. When I first set them, I thought "Looks way easier than V6." Then I tried climbing....not so easy....certainly harder than V4. Holding on to any individual hold was not difficult. Moving from hold to hold, different story.
I would guess V5 if spaced maybe 12-18" apart. Maybe V6 if spaced 24-30" apart (on a 45). This assumes heel hooks on the slopers or similar bad feet. Certainly ways to make more challenging.
You WILL want to use set screws. Otherwise, they will wiggle.
Whether setting problems at home, or just traversing, I use these a lot. I certainly use them a lot more than my Atomik medium sized slopers. They're just fun holds.
There are many holds and many hold companies I want to try. Of the 200ish handholds on my wall, XL sloper sets #1 & #2 are the only holds I would purchase repeatedly. 25 of these on my wall would not be too many.