After a long unsuccesful search on the net I must ask here:

I'm looking to convert 5-MeO-DMT freebase to fumerate to use sublingually.

I can't find a clear explanation of how to do it.

I have 500mg of 5-MeO to play with and plenty of fumerate.

How do I do this?

My experience is that sublingual can work but there is a better method IMO if you are able to accept that it is just a strategy for efficient administration and nothing else: Intra-rectal.
I tried 6mg 5-meo with harmalas at the same time and also 30 minutes prior with nothing past threshold.
I plugged 5.5mg alone and it was so intense I felt like I was heading towards another epic pharmahuasca of +100mg but there was an odd 5-meo-charactoristic strong euphoric push and the peak only lasted 5-7 minutes at that dose.

I just dissolved the 5-meo in 10:1 water to 5% vinegar. it was mildly irritating but just evaporating or vaporizing the water/vinegar off then dissolving in pure water would prevent that from the vinegar, though many chems are mild irritants themselves mind you. You could do the same with fumerate AFAIK.

Now if you are really opposed to plugging then pretty much anything that can be plugged can be snorted/insuffilated.
For accurate dosing doing this in liquid and the inhaling an aerosol/atomized or whatever (never done it personally) would be a the most logically safe method.

Just know that when administered efficiently, plugged or I assume snorted is very very intense similar to smoking it.

Thanks q21, but plugging isn't exactly what i'm looking for. That area is too delicate for other reasons to comtemplate that route. Snorting isn't a viable option either, and i really want to get away from smoking alltogether.

The reports I've read on sublingual use were very promising, and I simply need more time, not intensity.

Could you educate me on how to convert the freebase to fumarate?

Now I'm not a huge expert on this but to my understanding and alkaloid freebase is very easily converted to an acid salt when put in an acidic solution.
5-meo-DMT Acetate in Vinegar
5-meo-DMT Fumerate in Fumaric acid solution

Can't say for sure how much fumeric acid would be needed. Something like either 1 or 2 moles fumeric acid per mole of 5-meo-DMT
Not 100% on the stability of 5-meo but mine has oxidized but remained potent in the vinegar-water for several months.

You could do the calculations or just make FASW put the 5-meo-DMT in water then add the FASW until it is all dissolved (is freebase water soluble?)
Either way I think it would work. Just don't injest ridiculous amounts of fumeric acid and I think you'll be fine.

Just know that unlike with vinegar you cannot evaporate the fumeric acid off, it will remain.

I dunno, I'm pretty tired right now, hope it is clear as mud..

Thanks q21, i'll try FASA assuming 5-MeO freebase reacts the same as DMT freebase, and see how it goes.

FASA seemed to work converting the freebase to fumarate. Bio assayed a fleck of the fumarate and there's a slight baseline elevation.

I'll try a combination of harmala's and the 5-MeO fumarate sublingually next week or so.