ORIGINAL: seanreit
If you go the route I have gone, make sure you put a check valve on the line to the engine, you don't want heat coming up the line, it will fry the festo valve inside the engine.
Sean's got it bang on with check valve. I once had a small leak in an up stream fitting that was connected to a propane line, eventually causing the right-angle Festo bulkhead fitting to melt on that particular engine. The plastic in the fitting body melted away very quickly. The PST's use a metal fitting under the cover, but the polyurethane hose used on all brands of engines is also susceptible to melting with a short exposure to heated pressure casing air. An engine will only be exempt to that failure mode if it incorporates fittings with integrated check valves, likely the straight bulkhead union type that extend out the front of the engine cover. If the solenoid is left in and there's no integrated check valve on the engine, the solenoid is all that's preventing the venting. There's always a small chance the o-rings in the valve could become worn out or damaged one day, leaving the check valve as the last resort of protecting against a flow reversal. I recommend a check immediately preceding the solenoid, also used as the connector to the off-board canister.
Personally, I run both my jets with the canisters removed and have for a few years. On any auto start, I can't understand why a pilot would not be positioned in the immediate vicinity of his/her jet. For that reason, why not forgo the canister and opt for an external (and larger) version of the same thing? I do still include the solenoid and recommend that our customers do so, allowing the ECU to still ultimately control the flow. The rate of flow is determined by the trigger valve I use from Usher Tool.
One important note though for powermax canister users...
Powermax cans have a small clunk in them that allows the outlet to feed from the bottom of the canister, thus drawing liquid start fuel. In order to ensure gaseous flow only, make sure you invert the powermax canister. Most, if not all the engines today will require the propane or mix in its gaseous form only.
Here's a photo of my stingray and its propane valve position? The yellow line connects to the off-board canister through the check valve.
It's late...
Kelly