Lot's of guys in the Tacoma and 4Runner world use the 1700/1720/1750 rifle cases and they bolt them through to the rack.This allows for the case to be locked on the exterior and bolted to the rack from the inside, it is then not easily removable from the outside. The drawbacks of course are that it is no longer 100% waterproof, it is much more difficult to remove the case from the rack should you need/want to and of course you now have irreversible holes in a $200-400 case lol.
For my larger 1650 cases I simply run a ratchet strap north to south through the handles and over the top which holds it 98% of the way. I also run a simple bungee east to west which isolates any side forces and adds further down pressure, it also acts as an emergency backup hold in the case that one of the ratchet straps fails. I don't leave my cases on the roof unattended overnight so if I am to do an overnight in the city or at a hotel I simply remove them. This works for me especially when we are removed from society (the main goal) but it might be one step too many for some that never need to access the contents while on their trip (recovery gear and emergency gear). You can of course lock the cases themselves and it would be extremely easy to run a bike lock cable through the handles of the cases and the rack for further security.
I use one case for recovery gear and tools and the other for cooking utensils, dry goods/food and the skottle. Should I take more than two I can put clothing in one and the fourth can be used for bedding and miscellaneous items. Essentially I access all of the cases at some point in time during the course of my trips. I think those that permanently attach them via drilling method place items in them that they rarely need access to.
For my larger 1650 cases I simply run a ratchet strap north to south through the handles and over the top which holds it 98% of the way. I also run a simple bungee east to west which isolates any side forces and adds further down pressure, it also acts as an emergency backup hold in the case that one of the ratchet straps fails. I don't leave my cases on the roof unattended overnight so if I am to do an overnight in the city or at a hotel I simply remove them. This works for me especially when we are removed from society (the main goal) but it might be one step too many for some that never need to access the contents while on their trip (recovery gear and emergency gear). You can of course lock the cases themselves and it would be extremely easy to run a bike lock cable through the handles of the cases and the rack for further security.
I use one case for recovery gear and tools and the other for cooking utensils, dry goods/food and the skottle. Should I take more than two I can put clothing in one and the fourth can be used for bedding and miscellaneous items. Essentially I access all of the cases at some point in time during the course of my trips. I think those that permanently attach them via drilling method place items in them that they rarely need access to.