Christer built this 20m vertical out of thin-walled ventilation pipes. Thick ones at the bottom and thinner at the top. It uses top-loading wires to increase the capacitance.

Here is Christer's new TX using push-pull mosfets and capable of 500W or so.

Here you can see the LPF on the left, the divider board with o/p toroid below and the VFO on the right.