Yea you can jack up from underneath useing planks to spred the load but only only up to the floor to support it,then from inside the van you will have to remove the carpet and drill 8mm holes about 4 to 6 inches apart,and then go from there if you think the floor needs to have a piece removed,then you can say remove a small portion at a time,the glue you use to repair the floor is quite flexible,i drilled over 90 holes in my floor and removed some of it,i have now done the job and fitted a new carpet and it is as good as new,Good luck to you with your repair,