Firstly, good effort fella!
I'd like to see you keeping your weight on your heels, have the shins vertical and you sitting back and down a little (think DL) and driving through the hips with an aggressive yet controlled pop (just enough to get the bell where you need it).
The swing is all hips, hams, glutes and back, if you slow your cycle down and focus purely on sitting back and down little, firing with the hams and popping the hips (not hyper extending) then you should clear the full 21 depending on grip limitation.
Here's a vid of me with the 45kg bell. It was taken head on so you'll not get to see entirely what I mean but you'll see from the lean that the hips are way back and the drive is coming from the posterior chain, the bell is half or just over half my BWT so it takes quite a pop (for me) to get it overhead.
(n/wfs) explicit lyrics.
Hope this helps.