Glad you found it helpful. Your situation, motivated me to get my fingers working.
If you decide on that bunkie, once it’s fully set up, have either you or a helper take a video of the area under the bed while someone gets on it, or switch roles so one person gets on the bed while the you observe underneath. Watch for any flexing, even if it’s slight. The extra bunkie should solve the issue, but making this check will help ensure there’s no flexing and give you peace of mind.