I've seen some posts on TB asking about HSC's for FBasses. Part of the challenge is the unique Horns they have and they wont fit many cases without crushing some of the molding to make it work. I wanted to post in case helpful to others. I bought the below SKB open cavity case. I am very happy with this case. Its very sturdy and well made, comes with tsa lock. There is plenty of space and compartment I can put a humidifier in(I live in Denver) as that was part of my intent in getting cases. This will also come in handy for travel if ever I need it. I have a BN4 and BN5. The 4 string has a little more space, about an inch but I don't see that as being an issue. I can put a piece of sponge or foam in there to stabilize more. The only downside is its pretty heavy. Case alone is 22.5 lbs, so you are looking at close to 32 lbs with bass in it. Uploading pics to give you an idea. The BN-5 I bought post production online. The BN4 I had them make custom for me. Love them both.
iSeries Waterproof ATA Open Cavity Bass Case | SKB Music / ProAV
iSeries Waterproof ATA Open Cavity Bass Case
Model: 3i-5014-OP
iSeries Waterproof ATA Open Cavity Bass Case | SKB Music / ProAV
iSeries Waterproof ATA Open Cavity Bass Case
Model: 3i-5014-OP