I am still looking to perfect the gluten free pasta salad...  But this one is close! 
 Rice pasta penne is a difficult noodle... either they are too soft or they are super crunchy! 
 Oh the balance of the perfect noodle for a pasta salad... 
 The sauce is almost secondary I think... that said.. here is an idea for a perfect pasta salad! 
 I like Tinkeyada Rotini instead... they hold the sauce well and have a better texture when cooked... 
 Penne.. just don't do it for me.
Cook until al dente - and then stir and let sit for a bit.. they will continue to soak up water until the sauce is ready... 
 then dump and rinse until cold water until totally starch free... 
Let them drain completely. This is very important as the sauce will not adhere if the pasta if it is at all wet.

The Sauce:

You need:
1/2 cup mayo
1/4 cup sour cream
2 Tbsp mustard
dash of hot sauce

1/4 cup sweet green relish
1/2 cup peas
tin of tuna - well drained

2 ribs of celery chopped fine
1 carrot grated
1/4 of a small vidalia onion
 

mix the sauce all together and then pour over noodles... 

Eat and enjoy! 

The kids enjoy it and it is a great picnic item...