I'd suggest talking to a knowledgable paint store about how to prime and paint vinyl.

A good carpenter should be able to trim out the bottom outside of the window; every situation can be different. I've done it on such an Andersen window and it's just a matter of providing a base frame and applying the finish surface and trim. While there, be sure to insulate and air seal thoroughly.

Andersen bay windows are supported from above so the bottom brackets should just be decorative.

It shouldn't be hard to frame - want to make it a DIY project. All I need is a plan.

And I was hoping to learn by one's experience about painting the Anderson vinyl. I'd rather rely on that than what a paint store suggests trying. My experience is that a paint store likes to sell what they have, rather than what may actually be best for the window.

From what I've read, it's necessary to roughen the finish a bit, use a bonding primer (don't know what that is) and an epoxy paint. Just need a confirmation by someone who's done it successfully.

The product to prep it with is Wilbond. Wilbond makes the vinyl clean and tacky.
You will need to coat it within one hour after the Wilbond application.

Do not sand the vinyl cladding.

Paint with two thin coats of exterior 100% Acrylic Latex Enamel.

To prevent irreparable damage, chosen color must be no darker than the original color.

Michael

Thanks, Michael

The one vinyl window to be painted is white and sticks out like a sore thumb.... we'd like to make it a cedar color to match the other windows.

Would that create irreparable damage?

Here's what Andersen says:

Painting Andersen Products

NOTE: Although we state our windows and doors may be painted, Andersen® does not
warrant the adhesion or durability of the paint to our substrates.

NOTE: Matching the paint color for pre -finished interiors: Pre-finished interior
double-hung products use the same liquid vinyl system as the exterior vinyl finish
(Flexacron® vinyl system). Frenchwood Gliding Doors white PI have a vinyl laminate,
All other FW PI doors use the Flexacron system. Pre- finished white Casement stops are
wrapped in vinyl

Exterior Vinyl Surfaces
Colors and restrictions:
White vinyl units  may be painted any color with a Hunter L value
greater than 60 (approximately Sandtone color or lighter). Send color chip
to Andersen if unsure of color selection.
Terratone vinyl units  may be painted any color with a Hunter L value
greater than 40 (approximately Terratone or lighter).
Send color chip to Andersen if unsure of color selection.
Sandtone vinyl units  may be painted any color with a Hunter L value
greater than 40 (approximately Terratone or lighter). Send color chip to
Andersen if unsure of color selection.
Forest Green  Andersen does not recommend painting Forest Green
units.
Note:
The Hunter "L" value is used in conjunction with two other parameters
(hunter "a" and hunter "b") to describe the color of an object. In the case
of paint it is reflected color that would be considered. The Hunter "a" and
"b" numbers describe the hue of the color. Hunter "a" gives the color from
green to red and Hunter "b" gives the color from blue to yellow. The "L"
value is measure of the color's intensity; how light or dark the object
appears gives the color from blue to yellow. The "L" value is measure of
the color's intensity; how light or dark the object appears. The Hunter "L"
value for White is 85, Terratone is 35, Sandtone is 69 and Forest Green
is 26.
Send color chips to:
Andersen Corporation, Inc.
Attn: Customer Service Department
100 Fourth Ave North
Bayport, MN 55003
CAUTION:
Factory applied exterior silicone fillet beads may not accept paint.
Do not paint weather stripping, interlocks, jamb liners, patio door screen channels
or any surface that has an abrasive or sliding contact with another surface.
Solutions containing corrosive solvents should not be used on Andersen Perma-
Shield® (vinyl) products.

rub the surface to be painted with acetone, then apply a quality latex primer and latex paint. It's a pain in the a$$, but it can be done well if you take your time.