Using the 1.5x4 block on other maps than sf_crete, i managed to do some new, low blocklimit bases for:
sf_astrodome,
sf_canyon
and sf_overload
Here's the astrodome one built with 30 blocks.
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The front of the flag defense is double layered, and an eventual healer can avoid harm by hiding behind the 2x3's. Furthermore is it impossible to scroll-jump the flag defense, but it's still slamclimb able.

The wall is triple layered all way to the side blockers which are double layered, and i have used two 1.5 by 4 blocks as a ramp and as a part of the wall. The 2x3 i have placed outside the wall hides most of the wall when you are on the brigde, and a healer can hide there if a block has low percentage health.

You might spot on this last picture that i have placed a 1x5 by the spawner. The reason why i did that is that the spawner can be used as a straferamp, meaning you can easily get over the wall i made.
Canyon
30 blocks
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All walls are double layered except the 1.5x4's most to the right and left, which are single layered. Closest to the middle i placed the 1.5x4's in a way, that makes you unable to see the front part of the lower flag defense from the midfield. The blocks the walls are made of are also touching the ground which provides cover to healers.
The upper flag defense is approximately 3.5 units tall and therefore hard to double-rocketjump.

This picture shows the flag defense. It's impossible to slamclimb in a fight, and the front of the lower flag defense is double layered. Everything else is single layered.
Overload
30 blocks
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Here's the overload fort done with 30 blocks. It was a bit tricky, and i had to make the front flag defense a part of the wall. Sadly the front flag ended up as only triple layered. Anyway, the 1.5x4 and 1x5 walls are double layered, and all of the flag defense is single layered - apart from the front.
It is also impossible to simple rocketjump over the front/flag defense wall to get a touch.

The upper flag defense is hard to slamclimb, but it is easy to rocketjump in without hurting yourself too much, which makes it easier than the ordinary 35 Overload fort to double-rocketjump. Partly the reason for this being that the middle 2x3 (shown further down) of the flag defense needs to be placed so low in order to make it impossible to crawl in using the 1.5x4 walls.
The side walls points towards the spawn which makes those walls harder to shoot and see from the midfield.


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Any questions and critic with arguments are welcome.
Missunderstandings i will try to sort out too.