I'm trying to install a new tubular tire once again. The problem is every time I do this I always get it wrong because I always have this area (let's say 10-15cm each way) around the tire's valve that kinda extends a bit so when I ride after the installation I always have this wobbling, which you barely notice when you ride slow but when you speed up it's getting kinda annoying and a bit scary.

I watched A LOT of videos on youtube, I used different kinds of cements, tape and ways of installation, but I can't get it right for some reason. Maybe it's because I use cheap tires or I need to do something after the tire is settled on the rim?

Please tell me what am I missing here?