Context
So I have a Nikon 300mm f4 AF and may consider it's older but larger cousins the Nikon 400mm f3.5 or Nikon 600mm f5.6. I have a special pouch for the 300mm and it can easily fit in my backpack when I'm walking around. (I'm assuming that I'm not using the lens, otherwise it would be on my body.)
Question
Assuming I buy a heavier lens, what's the safest way to carry it in a backpack or in a checked bag? I measured the lens and they both clearly fit in my backpack, so I was thinking of leaving it at the bottom.
I do see special cases to hold the lens but I can't afford to check another bag. The fancy trunks are nice but yield the same problem, requiring me to check another bag.
I do understanding that padding is important but are there specific tips that relate with larger lens? I was imaging getting some fabric and wrapping that tightly around the lens so it can soften the blow but I'm unsure if that's enough or do teleprimes need more padding than smaller lens due to both it's weight and size?
This is similar to How to safely transport a camera and its lens from one place to another? except I'm focusing on larger lens which may require different backpacks or related. Many bags can fit and handle smaller lens/cameras but teleprimes are massive and not all bags may even fit them, let alone cushion them properly.