Keith,
The idea sounds appealing, however there is a very high usage of electricity in the electrolysis process to make the fuel. So when you consider the equipment weight, expense, and size, the process becomes impractical for RV use.
Remember, there is no free ride. Producing the electricity needed for the electrolysis process, and carrying the extra weight will require more energy (in the form of diesel fuel) than you will save in added MPG (miles per gallon).
The only way that the system is practical, is that you can use a smaller, more fuel efficient engine and depend on the hydroxi gas for extra power when needed instead of using a larger engine for the limited times that the extra power is required.
Gerald