Adding quality muscle mass does not inherently suggest loss of athleticism.
if you want to add 20 lbs in a month expect a good portion of that to be fat.
What are your goals and why is your vert. and 40 times applicable.
It would stand to reason that as you get heavier it will be increasingly difficult to keep these times and heights, UNLESS, you train very specifically for this.
Maybe need a little more info to fully answer your question vs. goals.