I don't get your numbers? Are you talking about a R3 or a R3T.
I did a lot of research on the subject before I ordered a Toyo Proxes4 245/50/16 for my R3.
The numbers I got came from the tire manufacture's web sites.
Stock Metz 240/50/16 20.07lbs
Toyo Proxes4 245/50/16 24.05lbs
for a difference of 3lbs 14oz
Yes, that will equal a power loss but not much.
I'll just make sure I take a sh*t before I take the R3 out.
I'll suck it up and do a dyno run for you guys. I already have a before dyno sheet.