Really, most of what makes or breaks a handspring front is power. Either you have enough speed in the run, enough punch on the board, and enough block, or you don't. It's hard to tell whether or not you have that from this short video, but to me it looks like you wouldn't with a springboard. How do you get more powerful? Conditioning. Handstand variations (presses, push-ups, holds, shoulder taps, etc) for the block, and plyos and squats (preferably with added weight) for the punch, spring training for the run.
Aside from that, there are two things that jump out at me. First, you're tucking too early, which cuts off your block. Second, you're staying tucked and never preparing for the landing.
For the first, focus on pushing the table down and forward as hard as you can, and getting the heels all the way over top. Try to keep your eyes on the table until your hands get all the way off it.
For the second, practice double fronts from a springboard. First, do them into the pit; when you can open up and land, do them onto a resi or a mat in the pit. This vault is very dangerous if you're just tucking and praying; you MUST have a strong handle on how to land a double front in order to do this vault successfully or even safely. If you have access to a decent trampoline and a coach who knows trampoline well, it would be a good idea to work some front one and three quarter saltos, as well as ballouts to your feet.
Also, cowboy. It is my very firm opinion that double fronts (and variants thereof, including handspring front vaults) should always be done with the knees separated.
When would you suggest I open up?
The fact that you are asking this strongly suggests to me that you are not ready to seriously train this skill, except into a loose foam pit (and even there, there are other skills I'd focus on first)
The exact timing will vary, but it's something you have to develop a feel for. There's nothing any of us can tell you that will help with this; you just need to keep working double fronts and drills for double fronts until you develop a feel for when to open out to land. Let me say again: THIS SKILL IS DANGEROUS if you don't know where you are in the air, and it looks and sounds like you don't.
Sorry if all that comes across as rude, but I'd rather you be offended by my bluntness than seriously injured because you have an inaccurate sense of your readiness for this skill.
To develop the air sense for this, work ballouts on trampoline (preferably with a coach who knows their trampoline stuff really well), and once you get the ballout to your feet, work it from a progressively lower bounce. Work double fronts into a loose foam pit until you are landing on your feet EVERY SINGLE TIME, then work them onto a mat in the pit until you are landing on your feet EVERY SINGLE TIME.
Until you have a very strong sense of where you are in the air on a double front, you should not even contemplate attempting this vault except into a loose foam pit.
, not too many people train this vault (usually tsuks and yurchenkos), so not too many other coaches have trained it before.
But how soon? I like your explanation of do it like I do a front tuck. I'll try to fix it, then I'll add a mat
