If you can do 2 elevated 1/4 wave 40m radials - do it.
It will give it a more uniform pattern, & may favor in direction or sides in which elevated radials are present.
With 2 elevated - you will be good to go. All set.
With mine, I set my vertical element length, 1st establish that - I did 20m so my vertical was about 16.5+-ft in length.
Then I made the radial long about 17ft - then started checking swr, cut off 1/2 inch of radial per time to get swr to 1.5/1.
Took about 4-5 trims to get there. All set. Hundreds of contacts. 73 K1WJ David