That will work fine. The comparisons of 703 vs 705 have been very well done elsewhere. I presume your 705 panels are straddling the corners? Do you have two in each corner, i.e. floor to ceiling? I hope so, more is better.
There is evidence to suggest that the foil covered product (either density) performs very well, particularly in that corner location. For a little extra performance you could fill the corner gap behind the straddling panels with loose attic insulation.
Best Regards, DD
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