The best example of this is/was made by Russ Stoltz at Challenge Tool, called a Husky Challenger...Fastest examples flown by Dennis Crooks in a P38 at the old Madera races..Two 8.8 twins, methanol fuel, C&H ignition, 2 Rimfire 1/4-32 spark plugs in each cylinder..Got kinda pricey when changing spark plugs between heats...The also made an 11.6 twin and a triple using 4.4 cylinders...the engines are museum quality, and the triple makes a sound like NO other....Another inline twin is made in Canada from 3.2 Sachs engines..Called a Merlin, very pricey....