Originally Posted by LeeD
If you want to add spin to what is now a flat serve, use slightly more backhand grip. You will lose ball speed for sure by adding spin.
If you need 70+% first serves IN, then you don't have a fast enough flat first serve to play at YOUR levels. If your flat serve goes in 40%, but you win 80% of those points directly from the serve, your first serve is plenty effective.
So... 80% of 40%=32% won, with 60% going to second serves... Which is probably anywhere from 40-60% won. So that's 24-36% won... So you have a 56-68% of service points won...
Say he win's 60% of his points with his first serve... 60% of 70% is 42%. 40-60% of 40% is 16-24%. So he wins 58-66% of service points.
His first serve is bound to win more points than his second serve, so the more he gets in, even if they are a fraction of a percentage higher in terms of point conversion rate, he has a better lower threshold of winning points.
For a pro, 80% of 70% is 56%. 50% of 30% is 15%. So a pro will generally win about 71% of service points. Someone with a good second serve however, 60-80% raises that up to 18-24%, totaling 74-80% conversion rate on service points.
In the end, it's all percentages and it's about a 2% difference in both directions, differing basically in how confident you are in your second serve effectiveness (hint hint). If you're more confident in your second serve (both in consistency and point conversion rate), obviously going bigger on first serves is better if you have a very good second serve to fall back on. Falling back on safer first serves to avoid hitting a terrible second serve is another good strategy to follow. Again, it all comes down to how good is your second serve.
On a side note, it's funny how I spit out these percentages and this conclusion, am very confident in my second serve (as long as I warm it up in the first game or two), and yet still strive to slow down my first serve for better percentages. Well, part of it is trying to conserve what's left of my shoulder and ease the burden by avoiding as many kick serves as possible.