Best way to handle transition in roof slopes?

I am planning to reshingle the front part of our house this summer to eliminate a couple of random leaks. Despite numerous attempts at repairs, I haven't been able to determine the source, so I've decided to just tear it all off and do the absolute best preparation and reshingling I can to fix it once and for all (basic 3-tab shingles).
Our main roof is 6/12 pitch which transitions to a porch roof that is a 3/12 pitch. I'm planning to install ice and water shield up past the transition point this time around, instead of the double-coverage roofing felt we have now. However, one area that concerns me is the actual joint in the roof sheathing (1/2" plywood) where the two slopes meet.
When I built the roof I used those little metal "H" clips between rafters for extra support. They work fine on the main roof, but the sheathing still flexes more than I would like at the transition point. I can't really install blocking there since I need to maintain airflow for venting under the sheathing, not to mention it would be a pain to install now.
In Tauntons book "Graphic Guide to Frame Construction", they show an extra layer of sheathing attached on top, to smooth out the transition for shingles. It sounds like a good idea, but I'm curious what issues it might cause. For instance, it seems like the upper edge of the add-on sheathing would create a "bump" where it meets the main roof. I suppose I could minimize that by using thinner 1/4" plywood, as this only serves to smooth and tie together the transition. I also wonder if this would cause issues at the outer edge where the metal drip edge of each slope meet.
How do you handle this?
Thanks,
Anthony
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Lay an additional strip of ice and water shield over the transition before you put down the rest of the stuff. That's all you need, and do the shingling on a hot day (not so tough a request!) so the shingles will more readily conform to the different slopes at the transition.
R
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Sounds like a workable solution. Thanks for the advice!
Anthony
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You're welcome. Have a happy 8th of July! ;)
R
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