Rick,
If you also have a tow vehicle, consider carrying the PC spare tire inside it. That will help your rear axle load significantly.
Model 2910T (T=Triple Slide) is Phoenix's heaviest rig. 2910D (D=Double Slide) is their 1st runner up. If your 2910 has 2 or 3 slide outs, you are spot-on driving it without fresh and waste water in all your tanks. 5-6 gallons of fresh water won't break the camel's back. It is nice to flush the toilet while in transit.
Your biggest concern will be a blowout which is most often an inner rear tire, especially one that does damage to the surround area as they sometimes do. You will want to keep your tire pressure at a full 80psi which brings up my next point. Do NOT blindly trust your tire gauge. What was supposed to be my best tire gauge turned out to be my worst, off by 9 psi too high. That meant I had 9 less psi than I thought.
CLICK HERE to read about it.
As far as a clean puncture flat tire is concerned, I carry a tire plug kit for roadside repairs. Walmart sells them for around $75, made by Slime. Toss out the green liquid Slime product itself and just use the from-the-outside-repair plug kit to seal the puncture. Then visit the next tire shop along the way to repair it better, or replace the tire if necessary.