Frank,
Unless you have the height to play with, (with 85'-90' at the apex to support 40M loops) the average height of the loops will make the take off angle inferior to a pair of 40M inverted vees. The pattern will be sharper and lower with the inv vees including high angle suppression.
I have a 3el 40M inverted vee wire Yagi supported at the 70' APEX level with the ends at about 55'. The avg height is about 63'. (Plus RF ground depth) Ask Huzman - we did a f-b test on Saturday against the NE Yagi and found the f-b was approaching -45db++. I found the average height "sweet spot" on 40M to be with inv vee apexes at 70' and the ends as high as you can get them. Phased inv vees shud perform as well.
If you have 85'-90' apex height to play with, then it won't matter if you use loops or inv vees.
Yes, I would go for an optimized 40M array there instead of 75M. You will be very competitive with the big guns and have much more fun on 40M with an array at 1/2 wavelength high above ground. On 75M, you will be less than 1/4 wave (avg) and back into the back of the bus. No fun that way.
Might as well be a lion for a day rather than a sheep for a lifetime....
T