Right,i've looked at the video,first question is on the vid it shows the puller angled towards the tip,is that right,secondly how hard is it to elasticate them,looks a pig...
There are a couple of ways to elastic side pullers. These are assuming the topkits are take apart, but the 2nd way will work with a telescopic top kit as well.
One.. is to go through side puller with elastic using diamond eyes threader if required, send elastic towards end of section where the number one fits, the number one section does not need to be fitted at this point, Thread elastic up the number one to come out at bushed end, Fit number one to number two, fit preferred connector to elastic at bushed end.
Pull elastic where it comes out of side puller,
remove diamond eyes threader , I then slide a tight fitting rubber buffer bead down the elastic to the side puller on topkit. This is to tension elastic, I then slide on a connector about 1.5" to 2" above this, and tie a knot in the elastic above the connector, The rubber bead is to either have elastic set tightish or soft depending on situation.
The 2nd method is to slide elastic all the way down from bushed end on number one section and down the number two section until it emerges from the bottom of that section, (again use diamond eye threaded if required.) The thread diamond eye threader through side puller but in reverse, the eyed end goes in first, thread it so it emerges from bottom of number two section. Insert elastic into eye on threader and pull back through the side puller, Again fit bead for tensioner and connector above that, as in Part one.
This method is the best way to do a telescopic section.It may seem long winded but only takes a few minutes.
If already elasticated and wish to change elastic , cut end off old elastic making sure what's left does not disappear into sections, superglue and of new elastic to end of old and pull old through kit until all new is inserted, cut ends off and fit beads etc as above in fitting new.