I dont know much about training aids and schooling gadgets so can you ride in side reins and if so how long do you have them and do you have any inside bend ? Also can you use them riding in a pelham?
But if you are not experienced with training aids etc, I would recommend getting an instructor to help you with fitting them.
The side reins should be the same length on both sides, they shouldn't be used to create a bend.
No - I would not use them with a pelham - only a snaffle. But then I would only ever be using them on the lunge and I would only ever lunge in a snaffle.
I'm also pretty anti side-reins Sugar Plum. They can, in the right hands, have a place on the lunge but I also feel very strongly that they shouldn't be used for ridden work.