Dig 9 holes, concrete those holes, carry some lumber.. Boom. You're $200 richer.

[100 bullets]

The card board tubes are not needed, I agree with other poster you don’t need to Mix and pour into cardboard tubes. Dig holes, pour mix into holes, add water & put your anchor bolts into concrete as it hardens. You’re speeding extra money on material and making job harder and longer for no benefit. Also if you ended up hitting rock you time frame is screwed