Hey Hiking, just wanted to chime in as I recently crossed over from Ativan to Valium, as Valium is said to be easier to taper off of and I wasn't having a great time with the first cut off of Ativan.
I would be interested in knowing how many times you dose daily, if it's just 1 dose daily - then yeah, doing half klon and half valium for about a week and then switching to full valium would be fine. Sedation is a normal side effect of the Valium AT FIRST. Feeling overly sedated doesn't necessarily mean that you're higher than what you need to cover the Klonopin Withdrawal. I agree with Insights in saying you'll probably need 10mg of Valium.
I dosed 3times daily with Ativan and and crossed over to Valium over the course of 11 days, I did feel sedated at first but the sedation wore off completely at around day 9 off the crossover. I will write up my crossover schedule for you so you get an idea of how I did it. Again, if you're dosing once per day this probably won't be necessary - but I'll draw it up as a reference in case anyone else needs it in the future.
My Morning Dose of Ativan was .4mg . . Mid day was .25mg . . evening was .25mg totalling .9mg - I found the valium equivalent to be 9mgs. Here's how I crossed over.
Day 1: .125mg Ativan 1.25mg Valium
Day 2: Same as day 1
Day 3: 2.5mg Valium
Day 4: Same as day 3
Day 5: .2mg Ativan 2.0mg Valium
Day 6: Same as day 5
Day 7: 4mg Valium
Day 8: Same as day 7
Day 9: .125mg Ativan 1.25mg Valium
Day 10: Same as day 9
Day 11: 2.5mg Valium
Once crossed over it's advisable to wait 2-4 weeks before you begin making any cuts to your dosage, as the Valium will continue to build up in your body to something like 5x your daily dose in the first month. Crossing over this way was, for me - basically a non event. It should be said that the success of your crossover and taper in general greatly depends on the state in which you begin. . . That is to say you should try to get on a dose where you're as stable as possible and hold there for a week before crossing over or making any further cuts.