I'd try to stick with some velvet on the back wall. You never get the projector perfect on the screen. The little bit of overscan fades into the bezel on normal screens. Also, there could be a little wander between power cycles that you normally don't notice but you would on the borderless. Finally, if you go with a 4K projector at 16x9 resolutions, the 17x9 panel is internally blackened out. You won't see this on normal screens but on borderless without good velvet on the back wall you'll see the light bleed on the sides.
Video: JVC RS4500 135" screen in pure black room no light, htpc nvidia 1080ti.
Audio: Anthem mrx720 running 7.1.4, McIntosh MC-303, MC-152, B&W 802d3 LR, B&W HTM1D3 center, B&W 805d3 surround, B&W 702S2 rear, B&W 706s2 x 4 shelf mounted for atmos, 2 sub arrays both infinite baffle: 4x15 fi audio running on behringer ep4000 + 4x12 fi audio running on 2nd ep4000.