[DeTomaso] 4 post lift jacks

[SEL]

hi all - have a 4 post lift with "jack trays" - these are metal trays that hang on the inside of each ramp via a side rail - you put the jack on the tray and lift car off the ramps in order to, for example, take off the wheels - the space between the jack ramp and the car jacking points in the front and back is 6" - what have others used for this application? Options so far:

1. really expensive tray jack from lift mfgr (anywhere from one-half to almost the entire cost of the lift) - also, min height is 8 inches...so not a perfect solution;

2. pieces of wood on the ramp to raise the car - seems less than ideal as the wood slipping or spinning may cause the car to go off the ramp;

3. bottle jack - can't find one with less than 8" min clearance required?

4. "bag" jack - this looks like a couple of small tires or rubber discs that inflate - this is the best option so far - cheap chinese version for $170 on ebay - usa brand (herkules) about $470.

Any other thoughts or suggestions greatly appreciated - thanks, stephen