I don't know how flexible 1/4" phenolic is but If it's very stiff, I wouldn't try to force it to bend.
On this riser the bloodwood accent is about 3/8". I started with a straight piece with the intention of bending it but it took alot of force to make it conform to the curve. I ended up cutting a curved piece. You can barely even tell the stripe is curved. It just follows the back of the riser.
My point is, I don't recommend 'forcing' things together. There will always be an equal force trying to pull itself apart. This could potentially shorten the life of the riser.
If you're going to use clear glass, I'd definatley use the air hose method.
If you're artsy and meticulos, you will find this very rewarding. Good luck and I hope you show pictures along the way.
Mike