Synthol is not the remedy for this problem, or any for that matter.
I first ran into this phenomenon in graduate school. A gym regular came over to me, struck a bicep pose and asked why they was so flat. After asking a few poignant questions about his routine the cause was clear.
The problem invariably inherent to those who have virtually no peak, but instead possess long, strong, tight and otherwise well-developed bicep muscles is quite simple and largely two-fold. Firstly, and most importantly, you are doing TO MANY full range of motion exercises. This type of regimen promotes the aforementioned development because you’re essentially stretching the muscle to greatly with every lift, consequently developing it with a stretched inclination. The proper remedy for this is partials (1/4, 1/2, 3/4s) exercises which work the bicep well within its more natural rounded manner.
Secondly, and although less important but still a problem, you’re likely not doing the types of exercises that profoundly enhance roundness. These include but are not limited, to REVERSE CURLS (curls wherein the palms are in the downward position), these are best performed with an easy bar or with various attachments on the cable machine, and specifically work the brachialis or small muscle beneath the bicep that protrudes outward like a little ball between the bi and tri. This muscle helps to bolster the bicep and augment the peak. (TO VIEW BRACHIALIS CLICK THIS LINK THEN CLICK AND DRAG THE ILLUSTRATION LINE TO “5” OR “6”…
http://www.getbodysmart.com/ap/muscu.../tutorial.html)
Another invaluable peak exercise that was heavily used and rightfully credited as being instrumental for this purpose by a guy with arguably the best peaks in history. Robbie Robinson was a huge proponent of the PREACHER CURL, an exercise so named because the apparatus severely limits your ability to cheat, should be a part of every bicep regimen. But remember not to use a full extension as is so often practiced in gyms, but rather use the mirror and when your forearm reaches the breaking point (about 135 degrees or midway between 90 and 180), stop and begin your accent.
I'm so sure excessive full extensions and the failure to properly employ these two exercises are your problem that I'd be willing to stake Marcus' life on it! Am I wrong?
Best to you.