That’s a good room dimension .
Set up on the long 35 ft dimension so there is a copious amount of space between you and the back wall.
Do you have a measurement mic? REW? If not, you may crawling for a long while and still probably mess something up.
If you don’t have measurement tools, try the following...Put the 2 subs along each side wall, 1 sub in front of listening position and 1 behind. Move each sub forward and backward from respective positions in small increments until a find the sweet paired spots along the side walls. Such paired placement will cancel out all the problem big nulls (for example, the widthwise ~37 hz, lengthwise nulls that might plague your spot). Perceptually, such relatively nearfield sub positions should also feel like you are floating in a uniform womb of bass...and provide just the right amount of tactile bass without it being distracting.
After you determine the right toe angle for speakers.... and with all that space behind you, you should be able to get some respectable envelopment and immersion from just stereo.
P.S. Also ensure that the subs you get have a variable phase knob, not some 0/180 flip switch (it is 2024).