sub box mounting

After installing a subwoofer box, it's my installation technique to mount the box to the floor of the vehicle in which it was installed.  I usually use L-brackets or something similar but I run into the same issue in most of my vehicles:

When hard-mounted to the floor it becomes impossible to reach the spare tire in almost all of my sedan installs, and some other vehicles.  I'm curious what other installers do in this case and if there are any other ideas.  I'm thinking it's just a 'give-n-take' scenario where the customer is gonna have to accept the fact that their spare tire won't be so accessible.

In SUV installs, I have a lot of customers ask that the box be removable so they can get the space back for the grocery run and such things.  The only thing I can do is warn of the concequences and make sure that on my install sheet, they see the "not responsible" clause.

Your thoughts-

On some vehicles all you need is one side of the velcro.  The rougher side of the velcro will attach to the factory carpet.  Just screw it onto the box and it should hold really well.

I guess you can see two levels to the dilemma.  One level is that the unfastened sub box becomes a projectile during a collision so they must be hard mounted to the vehicle.  The other level is that most of us live in the real world and we are more concerned about the sub box sliding around during the course of a normal drive than the danger of an unsecured box.

It is my personal feeling that if a box does not slide around during driving around, then it's okay not to be hard mounted to the vehicle.  If I'm in a collision, my LAST concern is the damage done by a box inside the car.  I remember the days of old when you drove a van and had everything unfastened just so that if you wanted something you could jam the brakes and it would hit you in the back of the head. 

In my own personal installation, I have the box in my SUV strapped with velcro on the bottom.  It doesn't slide around, but it is removeable.  But I'm persuaded by standards set forth by my mentors and certification body's, and industry rules, such as MECP, IASCA, etc. etc.,  that boxes must be fastened to the vehicle.  So, my dilemma, is that even though I have a feeling everyone lives in the real world, I have been installing to the highest standards I am aware of unless proven to myself otherwise that it is unnecessary.  I respect the opinions of most on this board so I am curious as to your install guidelines.