Brooklyn Bedding Kids mattress

I'm looking for a mattress for a young kid and saw the BB Kids mattress: https://brooklynbedding.com/products/bb-kids . Curious of people's thoughts on it. We have the Plank which we mostly like (although the sides have sunken a bit after a year). I was looking for reviews but now that I search it looks like they just released it.

Edit: I'm also worried about the fire retardant leaks someone posted about here: https://www.reddit.com/r/Mattress/comments/17vf2hu/brooklyn_bedding/

I think I want the following (don't know that much about mattresses):

• thin enough for a bunk (< 8 inches I think)
• medium-firm or possibly firm and later add a mattress topper if too firm
• fiberglass-free (I see some questions in reddit about non-woven silica as too but sounds like fiberglass is main issue)
• very durable for 5+ years even if kids jump on it (would prefer longer but 5 years minimum without losing firmness)
• not offgassing?