Just sharing my experience: I went through this last year when I was building out a rig for a three-week documentary shoot. I was obsessing over every gram because I knew I'd be carrying it all day. I actually tried the SmallRig Black Mamba Cage for Sony FX30 at first but found it a bit too restrictive for the battery door access, especially when I was in a rush. I eventually moved over to the Kondor Blue Sony FX3/FX30 Cage with Top Handle and found it way better for my specific workflow. Technically, the clearance around the battery compartment is much more generous, so you dont have to fish the battery out with your fingernails. It also has these nice 15mm rod mounts built into the handle which is great for mounting a follow focus or a monitor without adding a bunch of extra cheese plates. Another solid alternative if you want to stay light is the 8Sinn Cage for Sony FX3 / FX30. It is basically a skeleton frame that weighs almost nothing. I paired it with a SmallRig NATO Top Handle 2439 because it lets you slide the handle back and forth to balance the camera depending on your lens. Idk, having that adjustable center of gravity is seriously a life saver for low angles. The big lesson I learned is to always verify if the cage interferes with the top-mounted XLR handle pins. Some cages are a nightmare for audio. I would suggest making sure whatever you pick has a NATO rail on top so you can quickly strip it down for gimbal work. Anyway, hope that helps ur build!

Respectfully, I'd consider another option cuz honestly, I've had a different experience with those premium setups. I found them way too bulky and overpriced for what they actually offer... it was kinda a letdown.

• SmallRig Cage for Sony FX30 FX3 4183 (around $55)
• SmallRig NATO Top Handle 2434 (around $45)
• SmallRig Low Profile NATO Rail 50mm 1409 (about $10) This setup is way more cost-effective than the Tilta or Mamba rigs. The 4183 cage is super lightweight and honestly, the battery door access is way better than the Mamba version. I used a more expensive rig before and it was a nightmare to swap batteries mid-shoot. Just be REALLY careful with the aluminum threads though... they can strip if you're swapping things out too much. Not 100% sure if it's the best for heavy industrial use, but for a solid, lightweight setup on a budget? It's the best I've found. gl!!

sooo for your situation, i have used both and unfortunately had some issues. here is my take:

• SmallRig Black Mamba Cage for Sony FX30: basically the lightest option but i found the battery door access kinda cramped and annoying.
• Tilta Full Camera Cage for Sony FX30 V2: seriously secure for low angles but it is way heavier than expected. tbh i would be careful with the SmallRig one, it just felt flimsy... peace

honestly its so ridiculous how much these companies charge for what is basically just a shaped piece of metal. you spend all this money on a nice camera like the fx30 and then you gotta deal with this rigging nightmare. it drives me crazy that so many of these cages are either overpriced or just poorly designed... like why is it so hard to make one that doesnt block the battery door or feel like its gonna wiggle loose? its such a scam how they slap a pro label on stuff that feels flimsy or has sharp edges that catch on everything. i just want something reliable that actually works without having to sell a kidney, but it feels like the brands just dont care about the actual user experience anymore. its honestly such a headache trying to figure this out when every option feels like a total gamble.

Jumping in here because I've spent way too much time comparing the technical specs on these rigs. Regarding what #4 said about "honestly its so ridiculous how much these companies..." - yeah, the pricing can be a gut punch, but sometimes you're paying for those tiny machining tolerances that keep the cage from wiggling during a shot. We've covered the main budget and heavy-duty options, but if you're still worried about the battery door and want something that feels more premium than SmallRig without the Tilta weight, check these out:

• 8Sinn Cage for Sony FX3 / FX30
• This is probably the sleekest design out there. It fits the body like a glove and the battery access is totally unobstructed. Its way more ergonomic than the Mamba.
• 8Sinn Top Handle Scorpio
• This is a killer choice for low angles. It locks down super tight and you can rotate it 360 degrees depending on how you're holding the rig.
• Wooden Camera Sony FX3 / FX30 Unified Cage
• If you can swallow the price tag, the build quality is insane. Its basically industrial grade and wont flex even with a heavy lens attached. 8Sinn is usually my go-to recommendation for the FX30 because they actually think about where your fingers go. SmallRig is fine for most stuff, but if you want that "solid" feel, the 8Sinn Scorpio handle combo is a massive upgrade... just my two cents.