Part of the trick is Driver having skill with 4 reins. This means a GREAT DEAL of practice with reins only, and Tandem LESSONS from a skilled trainer with some experienced horses. Being a Tandem Driver is something that needs a lot of auto response, because things happen SO FAST you will die or wreck if you have to look at your hands.
With your two horses being so green now, I don’t think this is a good idea AT THIS TIME. It is a FINE GOAL for later after they are more experienced, and you have done YOUR homework to gain skills needed.
I am not trying to discourage you, but a lot of things need doing before you endeavor to use your horses Tandem. Your Leader needs to be BOLD, FEARLESS in any situation. They are going along “because they LIKE TO GO”, you really have little control if Leader doesn’t move forward. You can’t push them!! Your whip skills need to be good enough that you can “reach out and touch them” for needed forward if they hesitate or shy sideways. Lash on long stick whip is about 16ft for husband’s tandem whip. Can you hit what you aim at, both sides of Leader? Husband spent a LOT of hours gaining that skill, does pretty well now. Killed a couple bales of straw and spot targets on bale, perfecting his aim!
We did the cheapy tandem first, just got long traces, tandem keys, roger rings, trace carrier strap and long reins. Everything fit on our two single harnesses. Setup worked, looked alright, suitable and correct for show ring, road driving. These items just were not usable when we moved to more skilled needs doing CDE.
For the CDE we used home built Leader bars, not styled like antique leader bars. Those antiques will just knock your Wheeler silly with all that swing going!! Tjeerd Velstra has a driving book out with a section on Tandem. We modified our CDE harness after his, lead bars too. Lets us use shorter traces, no chance of trace on the ground to get Wheeler foot in, which HAPPENED with the long traces of original stuff. Everything was very useful in real WORKING conditions for CDE. Husband uses both horses or takes the Wheeler out of draft on straight-aways to let him rest. Our Leader works when ever he can let her, they both come into Vet check with the same temps and respirations! Saves the Wheeler for times when he is the only one pulling, like hazards or winding trail.
Not sure what bits you would be using, but strongly suggest you do NOT use pair bits with bars on the bottom. Yes they are traditional, look nice, but those bars can get snagged on shaft ends very easily. Few horses will relax to let you unhook the bar without exploding from being confined. The clear plastic tubing over shank ends of bit, will make a “bar” to prevent Wheeler hooking Leader reins. Yet plastic tubing will rip off bit if snagged on the shaft tip. Gavin Robeson with the Teams of Four, is shown with his horses wearing the plastic tubing to prevent problems. We did a wired bar on our first horses, never thought of plastic tubing then! Light wire bar would come off easily if snagged, but prevented rein problems with busy headed Wheeler.
Another suggestion is to start your hitching with string traces that can break. Lots of folks start with no traces for Leader, but our horses got confused with no trace barrier to feel. Didn’t know when to stop on the sideways! They were experienced Driving horses, so just light string trace to feel was enough, broke if they were not working together for safety. Horses have to learn to start together, with Leader staying AHEAD all alone out there. She did come back to visit the Driver a few times, Driver fumbled the reins and whip, then things would get straightened out again, retied the string traces again.
Tandem is not something you ever want to do alone. Again, you have a couple reins, whip, voice, for control and things can go bad in a heartbeat!! Always best to have a groom or friend that can help you, riding along or on the ground watching. I do a LOT of walking the first few hitchings, and this is with EXPERIENCED horses trying to figure out what we want of them. After they learn their job, things get easier, but learning times can vary!! Groom person may have to hop down to adjust things, pick up dropped whip, or run back to get whip still stuck in tree!! He SAID the tree grabbed the lash! Swinging that long length will get your lash tangled in the oddest places.
They don’t call Tandem Driving the most dangerous style with no reason! And the good drivers, trained horses make Tandem look SO EASY that people are fooled about the true skills needed. The skill standards do keep getting higher too! Totally amazing what they can do with their Tandems now.
Around here the Draft folk are known for some wild driving, they bounce the Leader off the ring walls, brag on how this is only 2-3rd hitching. Often use young horses, 2yr olds, because they go FORWARD, drag the Wheeler along. When they wreck it is bad.
Husband says he likes Tandem because the racing blood cleans out his arteries!! When the horses are good on marathon, it is like flying being behind a Cruise Missile!