Hi John,
I can see why you would reason that way. Blow molded bottles are very light, and so could tip over easily. Roto bottles are much heavier and stable as you will see when you get some of our new bottles in. The advantage of this design is to be able to fit the standard Hydraforce wall mounted bottle holder that many guys already have in their trucks and still accommodate the 7 qt. capacity that many guys want. Usually, when they are driving is when the tip over may occur and we've addressed that concern.
John