I think this has been discussed before but why is ascorbic acid-2 phosphate not viable as a topical?

It inhibits DKK-1. Was just wondering why it could not be used if it they were able to in this study?

http://www.ergo-log.com/vitchair.html

Arch Pharm Res. 2008 Dec;31(12):1652-8. doi: 10.1007/s12272-001-2164-4. Epub 2008 Dec 20.
Skin penetration and retention of L-ascorbic acid 2-phosphate using multilamellar vesicles.
Yoo J1, Shanmugam S, Song CK, Kim DD, Choi HG, Yong CS, Woo JS, Yoo BK.

Abstract
Transdermal formulation of L-ascorbic acid 2-phosphate magnesium salt (A2P) was prepared using multilamellar vesicles (MLV). A2P was either physically mixed with or entrapped into three different MLVs of neutral, cationic, and anionic liposome vesicles. For the preparation of neutral MLVs, phosphatidylcholine (PC) and cholesterol (CH) were used. For cationic and anionic MLVs, dioleoyl-trimethylammonium-propane and dimyristoyl glycerophosphate were added as surface charge inducers, respectively, in addition to PC and CH. Particle size of the three A2P-loaded MLVs was submicron, and polydispersity index revealed homogenous distribution of the prepared MLVs except neutral ones. Skin penetration study with hairless mouse skin showed that both physical mixtures of A2P with empty MLVs and A2P-loaded MLVs increased penetration of the drug compared to aqueous A2P solution. During the penetration, however, significant amount of the drug was metabolized into L-ascorbic acid, which has no beneficial effect on stimulation of hair growth. Out of the physical mixtures and A2P with empty cationic MLV resulted in the greatest skin penetration and retention in hairless mouse skin.

I see. Well would it be worth it for whatever is left over?

Sorry, I don't know.  I haven't really done much looking into it.  I have never read the full paper and didn't really do much reading on the hairloss boards either.  

After I read a few pretty pessimistic threads at HLT and HLH a while back I just assumed it was a lost cause.  But I don't recall anyone stating what the "significant amount" was exactly, so if you find anything that might suggest there is some promise for the treatment please post it.

A study suggested it would work if there is a transporter (sulfur), such as MSM at 8% or higher or DMSO.

I tried it and ultimately think it just wasn't producing any perceivable results.