Tested to scale up with the Kenko teleconvertor, it fails entirely and the solar disc couldn't be focused sharply, due to the very poor optics of the teleconvertor. So, the concept is not a problem but the implementation due to the poor lens. Sounds like a good telescope with a good eyepiece is a better bet.
Cloud covered very soon, hope I will be able to pump up the power to take some closeup active region shots!
I got it finally, but the sun was too low, poor seeing and transparency.
Also tested is the webcam trick, but the image is too bad for even pointing.