That's exactly where I place my jackstands when I have all four wheels in the air. As a matter of fact, as you may have noticed, you can usually lift both wheels high enough from one jacking point to fit a block of wood or something under the front wheel, then you can get the floorjack under the front crossmember in order to lift both front wheels (that is, if you don't drive it up on the ramps first).
My suggestion for a safe method of raising all four wheels, or rather, lowering the car from all four wheels off the ground: lower the rear of the car first, place the transmission in gear (if manual) and set the parking brake, then place wheels chocks behind each of the rear tires. You can then go around to the front and lower the front end. The front should stay high enough, before you move the car, to remove the floorjack without a need for additional ramping or blocks under the front wheels.
If you do not have the car supported on jackstands at all four corners, and only have jackstands at the rear while the front is supported by the ramps, either you had better chock the front wheels securely, get a helper to hold their foot on the brake, or lower the front of the car first.
I lowered the front first once and did not use chocks and the car started getting away friom me, heading for the garage wall! Luckily I had strength enough to save it before it hit.
