Welcome to the world of H16 cat sailing.
I purchased a used 80's H16 last year.
The mast came with bob float at the top. Well I tell you two of us had a job raising the mast.
After watching the video above I new something was a miss as I couldn't believe the chap in the video could raise the mast so easily.
The only thing I could factor in was the float. So I decided to take it off.
What a difference it makes I actually over compensated when raising the mast without the float and nearly shot off the front of the boat, the mast actually stopped me
Another point to make is that I do not have a mast step so what I do is balance / rest / hook the mast base foot under the small pin in the mast step I then tie a piece of rope to the mast through a cleat over the front beam and around the dolphin striker, I then cinch it up by employing a Trucker Hitch which is a compound knot consisting of an Alpine butterfly (Lineman's loop) and a hitch it basically acts as a crude block and tackle to tension the line. Tip do not cinch it up too tight as it could cause damage, but it does secure the mast quiet well when stepping.
As for the slack in shrouds, as previously mentioned the jib will take this slack up when installed. You could also use a lower hole in the shroud adjuster which is what I do, this also produces more mast rake.