Trouble is my wife was peddling twice as hard with regular fins to keep up. I would like to put turbo's on the Sport for her but have heard that the V1 drive well is not as robust as the V2 and may develop a crack if turbo's are used. Is this correct, the Sport is 5 -6 years old. If turbo's aren't recommended I will put square tips on instead.
You've done it now -- there is no turning back. There is no reason you can't convert the old Drive to Turbos. Cracking a sprocket is unlikely unless you overtighten the Allenhead retention screw (holds the mast in). The most common problem is the Allenhead not being seated properly and/or the screw backing out, allowing the mast to slip part way out and start wallowing the hole. Ultimately, this can throw the fin and ruin the sprocket.
This can be minimized by making sure you have a good seat on the mast flat spot, locking the Allenhead in place with a thread locker ( I use Loctite blue) and inspecting the screw and mast after each outing. If worst comes to worst, you can epoxy the whole mess in place using a good marine epoxy.
There are two elements that differentiate the V1 and the V2 Drives. One is the sprocket/mast combination. You can upgrade your old Drive anytime and continue using the same fins if and when you ever break your old V-1s.
The other element is drums and cables (must be replaced together because of longer cable lengths and different cable tips). This upgrade is quite a bit more expensive, mostly due to the expense of the cables. Most users don't have problems with the old drums and so it's not a big worry.
You can upgrade sprockets and masts
and/or drums and cables
independently. Most '08 Drives have V-1 sprockets and V-2 Drums; 09 and newer have V-2 versions of both.