To add to my earlier reply on delamination...all of the other adhesives did not 'stick' to the Tyvek enough to pull fibers out of the sheet. I wanted an adhesive that 'became one with the Tyvek' and didn't hinder flexibility. The contact cement satisfied this quest for me.
I actually did try some different tapes; Oh yea, they held just as you said. For the square areas or lengths I plan on connecting and the unusual shapes I couldn't justify the cost of the tapes. Plus the contact cement is a very thin liquid and I've been using different sizes of paint brushes to apply it with great success. I have now made 2 tarps, 1 tent and a backpack (like a moonbow gearskin.) The tie downs are 4" triangles that I used a 2" brush on yet the backpack has two 6ft by 5mm seams for draw strings I used a thin brush on; I would have used up one $12 roll of tape yet my $15 can doesn't look like I've used anything. Tape is faster and less messy yet unforgiving, 1 mistake and I pull out the scissors.