A while ago the Stabilia was the subject of PrewarCar Whatisit quiz. Someone was wondering then how many European makes had used the underslung concept. In America at least 6 makes had produced cars with an underslung chassis, of which the American and the Regal are the more well-known. Apart from the Stabilia I know of 4 other european firms using this concept.
The first was the english Phoenix Motor Co, which after having started with three-wheeled motorcycles (the Trimo and the Tricar) produced in 1905 the Quad car, a kind of four-wheeled motorcycle with underslung chassis.
Peculiar were the Amédée Bollée-like cooling units on both sides of the dashboard.
In 1908 a more car-like voiturette appeared, but in 1909 they changed to a 'normal' chassis. The second was the RMC, also called sometimes the Seabrook RMC after the Seabrook Bros, who sold the car in England. It was on the market from 1911, but was in fact a rebadged Regal. It seems to have been relatively popular in the UK, appearing in the colums of the magazines regularly. The underslung RMC lasted until just after the first World War.
Finally there were two british makes with underslung frame in the light car and cyclecar segment just before World War 1: the Adamson and the Taunton.
The Adamson was built by the Adamson brothers in 1913 and 1914, the history of which has been described by Michael Worthington-Williams in The Automobile of March 2003. The production of the Taunton was cruelly interrupted by the war. Only two cars seem to have been produced and a restart after the war failed.
Most underslung models were produced during only a few years, mainly before WW1. The Stabilia, the make with which it all started in 1905, would linger on for almost three decades under various names but without much succes until the end came in the early '30s.