Can't decide with regard to grammar options for son-8th gr.

I’d appreciate ya’ll’s advice. My son is going to be 14 and in “8th”next year. He’s been doing R & S 5 all year, but due to home situations, he’s only on Lesson 51 of 108(?). It’s been a very successful curriculm for him: he’s completely independent and learning what he needs to know in both writing and grammar (grammar comes easily, writing not all, but R&S has helped termendously). I’m concerned he won’t be finished with R&S 10 be the time he graduates! I know it seems sill yto me now, but as they get older, that thought does cross my mind.

The option is to change to Jump In and OMT since they will allow him to be finished within two years (except for the essay and research paper), as opposed to taking all the way to Level 10 in R&S for the rest of his HS’ling life. However, why change if he’s successful? R&S teaches writing in a way which is incremental and he’s getitng it without my being needed-a needed option currently.

Is Jump In and OMT rigourous enough? Is Jump In detailed enough in it’s instruction methodology? When looking at it, I thought it may be fine after he finishes R&S 5. Should I chance switching next year and it not be successful and cause him to drop further behind than he is currently (he should’ve been almost finshed with R&S 5 by now). 

What do you think? Thanks.