Minimum bend for hot air from Propex?

Thinking about where I'm going to put my Propex HS2000 heater. I've studied all the threads on Propex installs, including this one:
https://www.tnttt.com/viewtopic.php?f=54&t=72075&p=1271154&hilit=propex+heater+installation#p1254220
and I still am not clear on one thing:
How tight can I bend the OUTLET duct from the heater? Or, another way of asking, what is the minimum length I need to install the heater, from the propane fitting on one end to the bent outlet hose on the other?
eLink's install (from the previously cited thread) looks like he's using a 90-degree fitting on the INPUT side but a gentle bend on the OUTPUT side. I contacted Suremarine (NA distributor of Propex) and they strongly advised against using the Webasto W298-49A (https://www.suremarineservice.com/Heat/Duct-Wyes-Tees-and-Elbows/W298-49A.html?gclid=Cj0KCQiApL2QBhC8ARIsAGMm-KGBB1FFBMmL43IacAdy0Lzz8_ts9oNGJWo6Z1ErA3PoeYP_pgSyTMUaAmzUEALw_wcB) because the bend is so tight. The one eLink used, apparently available on eBay, looks to be less restrictive than the Webasto, but still . . . don't want to choke the heater and cause it to shut down.
On the other hand, both Tony Latham's and eLink's installs using a 90-degree bend somewhere in the outlet duct, so assuming that they're working OK, does it matter if the 90-degree bend is right at the heater?
While I ultimately plan to use the noise-dampening duct to carry hot air to the outlet port, I'm not against using the regular duct to make the bend outside the heater since I understand it can be bent to a tighter radius.
https://www.tnttt.com/viewtopic.php?f=54&t=72075&p=1271154&hilit=propex+heater+installation#p1254220
and I still am not clear on one thing:
How tight can I bend the OUTLET duct from the heater? Or, another way of asking, what is the minimum length I need to install the heater, from the propane fitting on one end to the bent outlet hose on the other?
eLink's install (from the previously cited thread) looks like he's using a 90-degree fitting on the INPUT side but a gentle bend on the OUTPUT side. I contacted Suremarine (NA distributor of Propex) and they strongly advised against using the Webasto W298-49A (https://www.suremarineservice.com/Heat/Duct-Wyes-Tees-and-Elbows/W298-49A.html?gclid=Cj0KCQiApL2QBhC8ARIsAGMm-KGBB1FFBMmL43IacAdy0Lzz8_ts9oNGJWo6Z1ErA3PoeYP_pgSyTMUaAmzUEALw_wcB) because the bend is so tight. The one eLink used, apparently available on eBay, looks to be less restrictive than the Webasto, but still . . . don't want to choke the heater and cause it to shut down.
On the other hand, both Tony Latham's and eLink's installs using a 90-degree bend somewhere in the outlet duct, so assuming that they're working OK, does it matter if the 90-degree bend is right at the heater?
While I ultimately plan to use the noise-dampening duct to carry hot air to the outlet port, I'm not against using the regular duct to make the bend outside the heater since I understand it can be bent to a tighter radius.