I have the Britax B Agile stroller, and I *think* I want to get a glider board for my 3.5 year old (we also have an 8 month old). We like to go on walks and explore the city, and our oldest is good for a while, but he gets a bit whiney and complains about walking sometimes, so I'm wondering if this might help. I see that there's a specific Britax version of the glider board -- is that my only option? Can I use a different brand? Anyone have experience with glider boards for this stroller that can give me tips?