Grohe tub filler connections

Have a Roman Tub filler (grohe) with handshower/diverter

These things all need to be soldered/sweated, so I will do 3/4" stems first into brass fittings.

I'm very handy, but haven't screwed up this kind of installation before...hoping someone else has! <grin>

1. Is it okay for connections to be 90 degree bends between valves/diverter
2. Will propane work on brass? Know many recommend MAPP (can I just use my Bernzomatic torch and screw on MAPP tank...or do I need to? (I will heat up copper first, then brass, as saw plumber doing that before)
3. The tub filler has simply a treaded rod below deck...into which a 3/4" tube fits, but am wondering if I can find flexible hose with fitting to screw onto threaded part (think this is risky as it'll be buried beneath deck), and then add thread adaptor onto outlet from diverter. If all copper is best, I'm fine with that too.

4. Special tips on soldering this copper to brass...don't care about speed of doing so. I'm good at soldering, and follow the 'rules,' but don't want to have to do this part over (at $900 don't want to be buying it again.)

Thanks folks. Newbie here so be gentle...albeit honest!

BTW, already read here that Grohe is a PITA...but my wife selected this and is even worse! <grin>

Cordially,

Doug

Brass is 60+% copper. Copper to brass is an extremely friendly combination to solder. I don't get the part about heating the copper first. You should put the heat mostly on the brass. By the time it is hot, the copper will also be plenty hot.

People have soldered brass over the years with propane. Plumbers often use acetylene. And now, MAPP is available . Some torches will use both. If you have the basic propane torch from the hardware store, the orifice and tip in that are probably not right for MAPP; but a new kit won't set you back too much.

The reason a hotter gas is better, is that time is your enemy here. You want to QUICKLY bring the metals up to temp., apply the solder, and DONE. If you have to keep the smaller, cooler propane flame on the jont for a long time to get to temp. this is when the flux burns off, and also the metal can become "unfriendly".

I am a plumbing novice and hated to solder copper until I used MAPP gas. It brns quick and I have a perfect bond everytime. Its worth getting this gas.
Be sure to remove the cartridges and rubber seals in roughs ins.
Chris

MAPP in Bernzomatic

So I'm in the hardware store and ask whether my propane bernzomatic top will work with MAPP...a guy sticks his head out from an aisle and authoritatively says that it will.

Went home and switched bottles and it did work...though frankly, I thought that the propane seemed better.

I ended up using mostly propane for the fittings...some of which were the wall mount elbows in brass.

I don't want to 'burn up' $900 in faucet fittings though, so is the issue with time of soldering just getting a bad joint or will too much time actually damage the fittings themselves?

D