On Saturday, November 16, 2019 at 4:51:21 PM UTC-6, Tango Whisky wrote:
With all these modifications, he will probably push best L/D from 44 to 44.5, plus he will be a test pilot for the reasons you cite.

And after the first contest he will have learned that it's not max L/D which matters, but L/D's at 90 ot 130 kts. At these speeds, a Kestrel basically falls out of the sky, regardless of any lipstick. Especially if the span has been increased.

My advice would be to sell this ship, and get one he'll fit in without making changes. ASW20 would be a good start, or Open Cirrus. Both are less, or significantly less, than 30k.

Having owned a 401, and I loved it, I regrettably agree with Tango Whiskey, other than the selling part . I'd look for ways to improve the L/D at the higher speeds. Adding tips doesn't change the wing thickness near the root and you have to push that through the air at the higher speeds, so I'm guessing with the wing extension the polars will still converge to something VERY similar at 80 kts or more.
Now for the great news. It's a fantastic glider with very pleasant handling that by it's nature teaches good flying habits. Go take it for a few x/c flights and then decide what you want to do with it. Turns out it's pretty well engineered for what it is. Yes, the airbrakes are somewhat ineffective but it has flaps/landing flaps and the descent rate is more than adequate. As a result, it lands pretty slow making the wheel brake sufficient if working properly. Get the drogue chute working and practice that if you really want to make a super short landing. Mine had one and I never did, though I do regret not doing it once at least.
A single, connected canopy would be a fantastic upgrade if done right and would eliminate the gliders weakest feature, where do you put the canopy while rigging on a windy day...
As to flying it, I focused on maximizing what the glider could do well, mostly by trying to minimize the time circling. Spend $60 and buy SeeYou and look at circling percentage for each flight. Select your thermals wisely and perfect thermal entry. Fly into cloudstreets or any lift lines at the lowest altitude that makes sense, and out the end high and fast. Enjoy the pleasant handling all the way, it's a fun glider to fly and a fantastic value.