First what we need is a relatively straight cut - without some stable cutting machine it can be difficult, but it can be done with ordinary 125mm grinder.

My favourite method is to put pipe on the vice that has jaws adjusted so pipe is about one third inside vice but can be rotated easily with left hand. Then I take grinder in right hand, placed it just above place where I want to cut it, then I rotate whole pipe while I hold grinder pressed steady on one position on pipe and make shallow circle on whole pipe circumference with grinder. Then when I marked where I want to cut pipe, it's far more easier to cut. With little skill, cut can be very straight and will need only minor finishing.

On pic I placed 2 pipes that were cutted with method above and I'm finishing it with grinding disc.

This are two pipes that are prepared with grinder & grinding stone - this two pipes will be weld to front strut brace to form triangular reinforcement - in next pics more details can be seen about this...

Now can be more clearly seen how triangular reinforcement will be joined with two pipes that are going to roll bar - they will be attched through hole that I made, just under the dash.

Duct tape is very handy with aligning pipes before welding.

This is how pipe joint looks like without preparation - this is immposible to weld correctly, of course, so I have to made some adjustments prior welding.

After some fine grinding and careful measuring two pipes are done - on pic there can be seen much nicer fit for good welding.

Even after many measuring and trying to be careful with checking for gaps I somehow "slightly" misjudged angle at two pipes that'll be joining, as unfortunately can be seen on left pic :-).

But, nothing that can't be solved easily with some welding ;-)

Not bad , I suppose that must be strong enough - welding penetration is excellent, as weld bead is relatively flat - I use slightly larger current on my arc welding machine.

Man, that helmet makes everything much easier!

Two pipes are welded in place and everything fits OK now.

After grinding to see penetration, I find it very good - everything is very even, with almost no slag. I guess with little excersising, I can make some decent welds in future.