Is there a way to turn this into a double swing arm mount?

Yes, you can add a second swing arm if you would like. The part number for that swing arm is RAM-109-1APU.

What screws are used to attach the RAM Mount to the gimbal bracket?

Typically the gimbal bracket included with your fishfinder will also come with mounting screws that should connect to the RAM® mounting plate. As these mounts are universal and are for many different applications, the necessary hardware needed for each application will vary. For marine applications, RAM® recommends stainless steel hardware to prevent corrosion.

Would this work for a hummingbird solix 12 fish finder 12” screen?

Yes, this will work with your Humminbird Solix 12.

Would the mount support a Garmin echomap ultra 2 106sv.? It is a 10” screen

Yes, this will work with your Garmin echomap ultra 2 106sv. 

Detailed dimensions of the following RAM-109V-1U, RAM-109VU, RAM-109H-1U. Not sure which one will suit my sounder positioning so the dimensions required before purchase.It is for a Lowrance Elite9 FS fish finder. Also just wondering if you ship to Australia? if yes could you please advise the cost. Thanks in advance for your assistance. GD

The RAM-109HU will work on your Lowrance Elite9 FS fish finder as well as RAM® Universal Marine Electronic Mount - D Size Short OR RAM® Vertical 6" Swing Arm Mount for Fishfinders & Plotters.
We do ship worldwide you just have to add to cart and proceed to check out to see shipping cost.

I need the two knobs that mount the locater too.

You can hit Complete Your Solution to see the compatible part for this Fishfinder.

What size are the adjustment knobs diameter or circumference

Both knobs are 2.37" OD

Will this attach directly to one of the adhesive bases that you sell?

The RAM-109HU is designed to drill in to a flat surface it is not compatible with the adhesive bases.

My unit came without screws & bolts. What size for the base plate?

We don't provide the drilldown hardware because we do not know what type of material it is being mounted into, but 1/4"-20 screws will work for the base plate.

Can you tighten the knob in order to have the arm in a fixed position

Yes, the tightening knobs of the RAM-109HU allow you to keep the swing arm in position on the horizontal drill down base as well as the chart plotter/fish finder at the other end of the swing arm.

I have a 2014 Tracker Proguide V17 SC and intend to purchase a Lowrance HDS Live 12 Fish Finder and have it mounted to the dash of the console but it appears without some kind of Ram Mount it will be a tight fit. Do you have a recommendation on which mount I need to purchase?

We have not tested on this specific boat but the base we would recommend with a relatively  small footprint would be the RAM-D-115-C. The base itself has a 3.68" diameter, so as long as there is a flat surface with that much area available to drill-in, that would be our recommendation.