Hope,
I apologize for not getting back to you sooner! We are traveling right now, so I haven't had a chance to get to the board until now.
Thanks so much for taking time to share more information about your son!

It really helps to get a fuller picture of where he is at skill-wise. From what you've shared, I think I would be inclined to place him in either Revival to Revolution or Missions to Modern Marvels. This is because placement in HOD is very skill-based, and correct placement makes a huge difference in how successful a child is in his/her guide.
Writing, grammar, literature, and spelling are a big part of HOD. This is because these skills are wound within all of the subject areas. Since our guides lean heavily in the Charlotte Mason direction in many areas, it helps so much if your child is comfortable with some of these skills gradually before working into the higher level of version of the skills later. We do want to place your son appropriately in writing, grammar, literature, and spelling to make sure that he gains the needed skills he is ready for in these areas.
So, with this in mind, I would encourage you to take a good look at Revival to Revolution and Missions to Modern Marvels to see which would be the best fit in the areas of writing, grammar, literature, and spelling. I would lean toward having your son do Revival to Revolution with Rod and Staff English 5 (as scheduled in Rev2Rev) and Drawn into the Heart of Reading Level 6/7/8 Student Book along with the Level 7/8 Book Pack (and the dictation passages we talked about earlier) along with the Wonderful World of Creative Writing as scheduled in Revival to Revolution as a 9th grader. Your son would also do the Exploration Education Physical Science Advanced Version (which is high school level Physical Science). He would do the inventor study as well. Both are scheduled in Rev2Rev. I think this would be a good fit.
If he did Rev2Rev as a freshman, he would need to add something for government (as he wouldn't get to that in our final two high school guides if he did Rev2Rev as a freshman and MTMM as a sophomore). We used A Noble Experiment for government with our oldest son by Zeezok Publishing. Your son could do this on your his free 5th day each week to earn 1/2 credit it government. If you did decide to go this route, then there is a thread I can link you to that will share with you how to count credit for Rev2Rev for high school. Your son would use Rev2Rev as is, except for adding government (possibly adding foreign language study and beefing up the Bible). Suggestions are given in the Rev2Rev for high school thread, if you do decide to go this route.
The reason I would lean in this direction is that I think it would fit your son's skill level well and still push him in many areas. The grammar will be daily and significant, while the writing will be more than he is used to as we write across the curriculum all throughout the school day. He would do copywork daily as well in a variety of subjects and do written narrations. The literature study through DITHR sounds like it will be a new set of skills too, which would be good. We want to solidify those important skills before jumping up into guides that assume these skills are in place.
The following year he could do MTMM with all of English 6 (as scheduled in MTMM), WWTB II for high school level composition (as scheduled in MTMM), and Drawn into the Heart with either some high school level classics of your own choosing or with a DITHR Book Pack instead. He would also continue with studied dictation. This Bible in MTMM is credit-worthy, and you would add Economics (and possibly Foreign Language). There is a thread that explains how to do this as well for high school, should you decide to go that route. This guide includes Chemistry, which would need some supplementing. However, we give suggestions for how to do this in the thread on using MTMM for high school.
Then, as a junior, he would do the World Geography Guide as written, and as a senior he would do the World History Guide as written.
This overall plan would give him the needed American history, government, economics, geography, and world history credits for high school. It would also give him Physical Science, Chemistry, Integrated Physics and Chemistry, and Biology credits with lab for science. It would give him a credit each year in English. Math would need to be at his level each year to earn a credit each year there. That takes care of your core credits of history, science, English, and Math. Bible would earn a full credit two years (from the World Geography and World History Guides) and a 1/2 credit in MTMM. He'd also earn 1/2 credit in logic, 1/2 credit in World Religion & Cultures, 1/2 credit in health, and 1 full credit in Fine Arts by doing the World Geography and World History Guide. He would gain 1/2 credit in foreign language in the World Geography and 1/2 credit in foreign language in the World History Guide too. I share this so you can gain a picture that it would be possible to follow this plan for high school and still have your son earn the credits he needs for graduation.
If instead, you felt MTMM was a better fit, you could go that route instead for his freshman year. Feel free to pop back and share your thoughts.
Blessings,
Carrie