in the next month i am doing a side mount coarse! I was just wondering what cylinders do you suggest for side mounting?
As several have said, or implied, the very precise, specific, and technical answer is, 'It depends.'
You are new to diving, I suspect you are looking at an open water sidemount course that will not necssarily involve overhead (hard or soft) environments such as caves / confined spaces, or decompression obligations.
What are you diving now for a back mount (single) cylinder? How does that trim out for
you? What exposure suit do you plan to use? What BCD do you plan to use? There are many options available, and it is hard to say that any particular option is wrong.
You could dive with two AL40s, to get a feel for the rigging of SM cylinders, and to practice gas switching. But, they are uncoomon in routine use because it is hard to see the benefit - for most recreational diving - of two AL40s over a single AL80. You could dive with two AL80s, because they are so common / ubiquitous in diving that learning how to manage them is a very useful skill.
You could use any of the cylinders recommended by other posters. You could dive with various steel cylinders - HP or LP, short or long, slim or fat, and whether or not they 'fit' you depends very much on you. Each respondent can tell you what we like - in my case AL80s or steel HP100s. Some of us can tell you what we start SM students off in - AL 40s, or AL80s, in my case.
I suggest you engage the instructor you are going to work with, and see what s/he prefers for training, and WHY.
gday guys! i started Scuba only this year
Good for you - pushing the envelope a bit, but with formal training. Let the Board know how the course goes.