Here are a couple of ways that builders have tackled wing jacks.
Brett Ferrell just bought these jacks from Greg Smith. They are adjustable with a max height of 53" and minimum height of 30". They're jack-screw based, so you just crank the handles. Check his out Velocityxl.com.
The 2 ton low tripod stands are the perfect choice for the mechanic who is working on a vehicle that is lifted by a two post lift or a four post lift. The adjustable 2 ton low tripod stand is used to offer additional support to either the front or the rear of the vehicle while performing service work on the two post or the four post above ground lift.
These jack stands can be placed between the runways of a four post lift and when the runways of the four post lift are lowered, the jack stands will support the weight of the vehicle. The wheels will be above the runway of the four post lift and wheel service can be easily performed.
These jack stands can be adjusted to various heights to offer additional support for a vehicle that is being lifted by an above ground two post lift. If you are pulling an engine or a transmission from a raised vehicle, you are changing the weight distribution. The tall jack stands will support the change of weight distribution.
Andy built his own using bottle jacks. You can check his out starting here.
From his blog:
Time to take care of a nagging issue. When I built my wing jacks, I didn't have the engine on and certainly no fuel in the plane. They worked great. Once the plane was assembled, they were on the edge of being too short. Most of the time I would struggle to get them under the plane; they were now too tall.
On the left is one of my new bottle jacks. They are two stage, telescoping jacks. They're one inch shorter than the old jacks.
When fully extended they have 1/2" more throw.