Off the ground

[Rowinatl]

I just purchased my very own Concept2 this weekend and have noticed that when I go all out, the rower seems to burp (the sound) and lift slightly off the ground. I've never noticed this on any of the other C2s I've used. Additionally, I am only able to pull a 1:29 or 1:30 when going all out which is slower than I can do on other Model Ds at the same df. Not a huge issue because I am only going all out for a sprint finish, but would like to know if it is because I am too fat, bad form (perhaps I am pulling hard with my feet on the recovery), or something with the machine (also, it is on concrete and not a mat or carpet).

Thoughts?

Thanks!