Body mass/size is totally irrelevant to stamina, it's dependent on fitness (and on rare occasions genetic quirks).
Look at the very top-rank marathoners. Bicyclists. Long-distance skiers. Any serious, serious endurance sport. Triathlons.
Body mass absolutely limits endurance. Eventually.
On the other hand, the whole "big guys are slower" thing, that's been disproved by many, many heavyweight champion boxers. And the big MMA guys. Their endurance on the long haul may be less than an equally fit person of smaller stature, (Ali will never catch Wilson Kipsang on the 10k), but Muhammed Ali was juuuust as fast as anyone 30 pounds lighter than him. Faster. Guy was crazy quick.
Fast-twitch muscle fibres work differently than slow twitch muscle fibres and an extra fifty pounds doesn't seem to matter that much to them. Ali, Feodr, lots other big guys have been quicker than their smaller opponents.
That said, the far extremes of size and bulk - Andre the Giant vs Aditya Dev, world's smallest bodybuilder..sure, I guess Aditya could maybe outrun Andre? I have no idea.
The Body Type Modifier is a bit much at the upper end. It means you can take repeated 9mm hits, reliably. Muscle mass shouldn't determine that and, as a consequence, we never figured it did. BOD and Body Type Modifier also measure your toughness, your stamina, your resistance to pain. Terminator had a high BTM, ( SDP, really, but I digress) but Mad Max would be as high or higher. Guy just wouldn't die.
Problem was the lift values were -also- based on your Body stat and that meant every Tough Guy also has to be a Strong Guy. Bit of a fail, there.