While the Lorch Birds look like early planing boards (and I am sure they are), the Ultrasonic no doubt will plane earlier.
Comparing the small 149 Bird to the US 147. The US is 19 cm wider, .2 kg lighter and will carry a fin 10 cm longer. I agree with Roger, length is a "drag".
If you go to the two larger Birds, 164 & 179, they get wider 80cm and 88cm (Ultrasonic 93cm) but they get heavier and longer too. At some point, more volume (and weight) only hinders early planing, unless you are a heavy weight sailor.
If you like your 69 cm wide and 130 liters for early planing, you haven't really experienced early planing.
For an sailor in the 75 to 85 kg weight range, I would guess the US will plane earlier than any of the Birds.
For early planing on any board, good pumping skills is critical. If I was on my formula board and a 9.2 sail in a steady 8-10 knots (a few small white caps begin to appear), I would never plane if I didn't pump, but three good full body pumps (legs too against the fin) and the board will be moving at 16-20 knots of board speed within 5-10 seconds. I weigh 77 kg, I also have an 11.0 sail and with it, the same will happen in 1-2 knots less wind.
Formula 160; iSonic 111; HiFly Move 105; Tiga 263; '85 Mistral Superlight.
Maui Sails TR 11.0; 9.2; 8.4; 7.6; 6.6; Maui Sails Switch 6.0; 5.2; Maui Sails Global 4.5; 4.0.