Jora, my GSD was pretty fast. In fact, at one of the last CPE trials I ran her, she was 9 years old and her and a 10 year old BC were the two fastest dogs of any height in their level (Jora being just a second or so faster than the BC). This is her...
Jora isn't oversized though, she's 23" and about 62lbs. I agree that the reason you don't see heavy dogs competing as much is because they often aren't great jumpers. This isn't just giant breeds but also breed which tend to be shorter and stocky. The biggest issue with such dogs I have seen is that they often knock bars, some even when they are run in preferred, which is a jump height lower than what they measure at.
I feel the reason you don't see more GSDs excelling at agility isn't so much a size thing but a drive issue. A lot of the GSDs I have seen competing are just doing because their owner is asking them to, they seem to have no drive for it though and just trot around the course. Also some are just not built for it due to physical exaggerations that have been selected for. My male GSD was driven enough but jumping was awkward for him due to the length of his rear legs.
Jora isn't oversized though, she's 23" and about 62lbs. I agree that the reason you don't see heavy dogs competing as much is because they often aren't great jumpers. This isn't just giant breeds but also breed which tend to be shorter and stocky. The biggest issue with such dogs I have seen is that they often knock bars, some even when they are run in preferred, which is a jump height lower than what they measure at.
I feel the reason you don't see more GSDs excelling at agility isn't so much a size thing but a drive issue. A lot of the GSDs I have seen competing are just doing because their owner is asking them to, they seem to have no drive for it though and just trot around the course. Also some are just not built for it due to physical exaggerations that have been selected for. My male GSD was driven enough but jumping was awkward for him due to the length of his rear legs.