+1 about the tape. In about 2 years the strip of tape on the bottom will mostly come off and be left dangling down from the bottom of the canvas. It's never a pretty sight.
IF you are interested in your canvas remaining perfectly level on the wall for eternity, you might look into a scheme like you see with these
WallBuddies. You level the frame by shifting it left and right, so the two nails don't have to be exactly the same height.
If you can find simple sawtooth hangers about 4" long and with holes big enough for #4 or #6 screws, a pair of those positioned at an angle will work just as well for canvases weighing up to several pounds.
In truth it must be said that asking your average art buyer to put TWO nails into the wall at roughly the same height can be a stretch for them. And that's on top of asking them to use a tape measure, and do fractional math. So you need to provide detailed written instructions, and set things up so that all measurements come out to either even-numbered exact inches, or at least inches and a half.
Now, here's where it gets non-linear. You should position one of the sawtooth hangers so the teeth can engage the nail. But mount the other sawooth upside-down so the SMOOTH part rests on the nail. Why? Because every type of frame is going to stretch and contract and warp during its lifetime, which can pull the nails sideways and undermine their grab into the wall. The upside-down sawtooth provides a low friction bearing surface, while the tooth-engaged sawtooth maintains registration. That expansion and contraction is why I no longer use WallBuddies, but still approve the angled sawtooth concept.
Notice the picture for the W3300 WallBuddie shows them installed backwards. Stupid photographers!
Or you can just put two d-rings on the vertical sides. But that requires exactly positioned nails, label that "difficult for your average Joe Art Buyer."