A side view of a Tyler tile, cut through the vertical centreline and drawn to scale in mm. Change the front lip and wall thickness to see how much of the panel you actually get to look at.
Visible screen < panel
The front lip overlaps the panel edge by the lip width. It first covers the panel's own black border; only once the lip is wider than that border does it start to eat into the active (picture) area.
Flex tail needs room
The flex/ribbon tail must fold inside the enclosure. The U-bend sticks out past the panel edge and may force extra depth behind the panel and a wider frame on that one edge, so that edge can't be borderless.
Layer thicknesses are typical / approximate, not measured from a chosen part, unless noted. Cover glass 0.7 mm (4″) / 1.1 mm (10″); LCD cell + polarisers 1.4 mm / 1.8 mm; backlight 1.5 mm / 2.5 mm (so the 4″ module is ~2.9 mm and the 10″ ~4.3 mm, inside the 2.5–4 mm and 3–5 mm typical ranges). For reference, the CDTech S040HWV09NN datasheet in the research sheet lists a thinner 2.30 mm module.
Flex: 0.2 mm thick, bonded at the back of the cell, bends around the backlight edge and returns behind it. Minimum centre-line bend radius is whatever it takes to clear the backlight (about 1.2 mm for 4″, 1.8 mm for 10″); a larger chosen radius pushes the return run further back and adds depth. Return run length ≈ tail length (40 mm for 4″, 50 mm for 10″) minus the bend.
Board: Pi Zero-class, 30 mm across the section, 5 mm tall including parts. Battery: flat LiPo, 34 mm × 6 mm (4″) or 50 mm × 8 mm (10″). 1 mm is left behind the flex for the connector, 0.5 mm before the back cover, 0.2 mm between lip and glass, 0.3 mm side clearance.
Panel geometry from the research sheet: 4″ = Youritech ET040HD20-K (active 71.8 mm square, outline 77 × 80 mm); 10″ = Youritech ET100SQ01-GX (active ~179.6 mm square, outline 186 × 192 mm). The panel's black border is (outline − active) ÷ 2 per side, assuming the active area is centred. The tail edge is the bottom edge in the front view. Diagonal inches = side × √2 ÷ 25.4.