The mat will be good for your deck, but it's not strong enough by itself for the stringers. Normally mat is alternated with woven roven over the stringers.
In the early days lots of boat stringers were done with mat and the boats did fine structurally...it's strong but not as strong as woven material. Using all mat just isn't efficient and gives a more brittle lamination compared to alternating it with layers of woven cloth. It uses 2x the amount of resin that woven cloth does per fabric oz, which mean heavier too. Best practice is to do mat/woven roven/mat...etc. You don't want to do only woven cloth either because it is too flexible by itself.
