Making an existing HW timber frame stronger against uplift

We plan on using the Extenda bracket s to lift the proposed carport over the existing roof.

Given the age of the nails holding the frame together is adding extra hold down strength to the top plate warranted ?
Is the brace ply sheathing going to be strong enough
If it isn't what is going to be the most cost effective way of doing so?
I was thinking of those 3mm steel "L" brackets sold to hold benches down to concrete floors and 12mm coach screws or 14G self drive as these are cheap and strong unless a standard triple grip would do the job.
The engineering specs for the brackets say that the limiting factor is going to be the structural strength of the frame and they make the assumption that the rafters are held to the top plate and stud to top plate with 3 nails [ I assume this it to make an allowance for deterioration in hold down due to age]


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