single axle drive with tag/pusher axle

Long story.
When I converted the truck I was working with a company that had really light freight. 15K was heavy. i would pull the front axle up on the truck, front axle up on my curtain trailer and would average 8 on a trip from central SC to central CT. LOVED IT. Would haul gross weight for another company 2-3 days a week. LOVED IT.
I converted mine myself , so that if I wanted to change back, I could. No Volvo parts were harmed during the making of this truck. I modified all the bolt on "conversion parts" to fit the truck.After all these years, I converted it Back to Tandem drive. I almost cried when I took all my pride and joy out from under the truck and become "ordinary" again.Simply reason is that my light weight gig went away , and I started pulled max + weight everyday into hill country. The 20K rear finally wore out the rear , and I thought that by going back to a tandem it would work better with the daily gross weight work. Loaded both ways max 2-4 days a week. Max one way , all 5.
Upsides
1.couple hundred pounds in weight saving
2. Fuel economy
3. Less Toll money
4. Simple lift made with 2 inch winches(welded on) and 2 inch strap
Downsides
1. increased tire wear (fuel easily covered this)
2. increased wear on rear ring and pinion
3. increased carrier bearing wear ( i added a bearing, directly over the lift , so that it I could keep shorter driveshafts , and to make sure that when the axle was lifted, it didn't interfere with the driveshaft. On paper the axles and the lengths were all within proper limits , but she did like to eat a carrier bearing every now and then.?
4. Traction in some limited occasions. I don't do the 4x4 #### some folks are asked/required to do , but in snow , you had to pay attention. Remember though, that I was always light in deeper snows. I had a dump for just the front axle in the cab , so I could throw a little weight around when needed.

Truck is a Volvo 610 with roof fairing, 48 ft conestoga trailer with spread. 500 HP series 60 with fuel turned up. 13 speed, low pro 24.5 rubber.

My recommendation is that is is a fantastic upgrade. The truck though, must be matched to your freight situation.Worked beautiful for years in the right application, Not as good, but still worked in the slightly less than optimal application. No magic bullet, just more food for thought. Sorry.