Cracked Shower Pan

I have a 2017 T@b 320 Boondock with a shower pan that has developed multiple cracks. I previously repaired two cracks a couple of years ago by drilling small holes and applying Flex Glue. Recently, I discovered a new crack.

I believe the cracking is due to a lack of support under the pan, exacerbated by the weather extremes in my area. An RV technician I use for more complex repairs suggests a repair method that involves drilling holes through the pan and filling the void underneath with up to three cans of expanding foam. After the foam hardens, he trims and smooths the excess. He claims this provides support and is waterproof.

I am concerned about potential damage to any mechanical parts located under the pan and toilet area. I would appreciate any thoughts or experiences others have had with this type of repair. Thank you.